A Complete Insight into Real Glow Squid: Technical Specifications, Grades, and Applications

Types of Glow Squids

A glow squid is a fascinating deep-sea cephalopod known for its ability to produce light through bioluminescence, a biochemical process that allows certain marine organisms to emit light in the dark ocean depths. Most glow squids inhabit mesopelagic to bathypelagic zones—typically between 300 and 1,000 meters (1,000–3,300 feet)—where sunlight barely penetrates. Their bioluminescent capabilities serve multiple purposes, including camouflage, communication, predation, and predator evasion. While not all deep-sea squids glow, several species have evolved remarkable light-producing features. Below is a detailed overview of notable bioluminescent and related squid species.

Ommastrephidae Family Squids

Members of the Ommastrephidae family are among the most widespread and ecologically significant squids. While not all species are bioluminescent, many possess light-producing organs (photophores) or chromatophores—specialized pigment cells that allow for rapid color and pattern changes. These squids are found in tropical and subtropical waters across the Pacific, Atlantic, and Indian Oceans.

Key Features

• Wide global distribution
• Advanced chromatophore system for visual signaling
• Some species exhibit bioluminescent patterns
• Important role in marine food webs

Limitations

• Not all species are truly bioluminescent
• Limited research on deep-sea variants
• Short lifespans in most species

Best for: Ecological studies, understanding cephalopod evolution, marine biodiversity research

Jumbo Squid (Dosidicus gigas)

Also known as the Humboldt squid, this large, aggressive predator can grow up to 5 feet in length. It is primarily found in the eastern Pacific Ocean and is known for its deep-diving behavior, reaching depths of 370–700 meters (1,200–2,300 feet). At these depths, it emits a faint blue-green bioluminescent glow, likely produced by symbiotic bacteria in specialized photophores.

Advantages

• Pronounced bioluminescence in deep waters
• Used for counter-illumination camouflage
• Active hunter with complex behaviors
• Well-studied due to commercial importance

Limitations

• Glow only visible at extreme depths
• Aggressive nature limits observation
• Vulnerable to overfishing

Best for: Deep-sea ecology, predator-prey dynamics, bioluminescence research

East Pacific Red Squid (Elasipodida)

This deep-sea squid species is known for its unique interaction with light. While its body reflects red light—making it nearly invisible to other deep-sea predators—it also emits blue bioluminescent flashes in a pulsating pattern. This luminescence is often triggered by stress or during mating displays, serving both communicative and defensive functions.

Advantages

• Specialized red-light reflection for stealth
• Controlled blue bioluminescence for signaling
• Effective predator evasion in dark zones
• Unique dual-light interaction strategy

Limitations

• Less intense glow compared to other species
• Limited geographic range
• Rarely observed in natural habitat

Best for: Studies on camouflage, deep-sea communication, and evolutionary adaptations

Blood Squid (Eledone cirrhosa)

Also known as the common octopus or horned octopus, Eledone cirrhosa is not a true squid but a closely related cephalopod found in the colder waters of the North Atlantic and Arctic Oceans. Despite its nickname, it does not exhibit bioluminescence. Its red flesh and blue blood (due to hemocyanin) have led to speculation about potential evolutionary pathways toward light production, though no functional photophores have been observed.

Scientific Interest

• Model for studying cephalopod physiology
• Contains hemocyanin, a copper-based oxygen carrier
• Potential evolutionary precursor to bioluminescence
• Adapted to cold, deep environments

Limitations

• Does not produce light
• Misleading common name ("Blood Squid")
• Not a true squid (belongs to Octopodidae)

Best for: Comparative anatomy, evolutionary biology, non-luminescent cephalopod studies

Vampire Squid (Vampyroteuthis infernalis)

Despite its name, the vampire squid is neither a true squid nor a vampire—it's a unique cephalopod occupying its own order, Vampyromorphida. Living at depths exceeding 600 meters (2,000 feet) in low-oxygen zones, it uses bioluminescence in extraordinary ways. It can eject a cloud of glowing mucus to confuse predators and has light-producing organs (photophores) on its arms and body. Importantly, it exhibits true bioluminescence, not biofluorescence.

Advantages

• True bioluminescent capabilities
• Unique defense mechanism with glowing mucus
• Thrives in extreme oxygen-poor environments
• Living fossil with ancient lineage

Limitations

• Frequently misunderstood as non-luminescent
• Difficult to study due to deep habitat
• Slow metabolism and limited mobility

Best for: Deep-sea adaptation research, bioluminescence mechanisms, evolutionary biology

Species	Bioluminescence	Depth Range	Primary Function	Habitat
Ommastrephidae Family	Some species	200–800 m	Camouflage, signaling	Tropical & subtropical oceans
Jumbo Squid (Dosidicus gigas)	Yes (blue-green)	370–700 m	Counter-illumination, hunting	Eastern Pacific Ocean
East Pacific Red Squid	Yes (pulsating blue)	500–1000 m	Communication, evasion	Deep Pacific waters
Blood Squid (Eledone cirrhosa)	No	100–1000 m	N/A	North Atlantic & Arctic
Vampire Squid (Vampyroteuthis infernalis)	Yes (mucus & photophores)	600–900 m	Predator evasion, defense	Global deep-ocean zones

Expert Tip: Bioluminescence in deep-sea squids is often the result of symbiotic bacteria living in specialized light organs. Understanding these microbial partnerships can provide insights into both marine biology and potential biotechnological applications, such as natural light sources or medical imaging tools.

Note on Terminology: "Glow squid" is not a formal taxonomic term but a colloquial name for bioluminescent cephalopods. True bioluminescence involves the production of light via chemical reactions, while biofluorescence involves absorbing and re-emitting light. The vampire squid, despite myths, is indeed bioluminescent, not merely fluorescent.

How to Use Glow Squid: Applications Across Industries

Glow squids—deep-sea cephalopods known for their natural bioluminescence—are more than just fascinating marine creatures. While primarily inhabiting the ocean’s twilight and midnight zones, their unique biological traits and physical characteristics have led to diverse applications across culinary, scientific, aquarium, and traditional medicine fields. Whether utilized in their living state or after harvest, glow squids offer both practical and aesthetic value, though many of their purported benefits remain unverified by modern science.

Culinary Uses of Glow Squid

Glow squids are increasingly featured in global cuisines, particularly in coastal regions and high-end seafood restaurants. Despite having no scientifically proven health benefits, they are prized for their delicate texture, mild sweetness, and visual appeal—especially when their bioluminescent properties are preserved during preparation.

In Japanese and Korean cuisine, raw glow squid is commonly served as sashimi, thinly sliced and presented over ice with accompaniments like wasabi, soy sauce, pickled ginger, and daikon radish. The dish highlights the squid’s fresh, slightly briny flavor and tender consistency. For cooked preparations, glow squid is often:

• Grilled: Cut into rings or left whole, seasoned with salt, pepper, and citrus, then seared over high heat until lightly charred and tender.
• Stir-fried: Quickly sautéed with garlic, chili, vegetables, and savory sauces such as oyster or teriyaki for an umami-rich meal.
• Used in pasta: Incorporated into dishes like squid ink linguine, where their natural pigments lend a dramatic black hue and a subtle oceanic depth of flavor.
• Slow-cooked: Simmered in broths, soups, or stews—such as Korean jjigae or Mediterranean cioppino—to infuse rich, savory notes into the liquid base.
• Stuffed: Filled with rice, herbs, and spices, then baked or poached for a hearty entrée.

Their porous flesh readily absorbs marinades and seasonings, making them a versatile protein in Asian, Mediterranean, and fusion cooking. However, overcooking can result in a rubbery texture, so precise timing is essential.

Scientific Research and Bioluminescence Studies

One of the most valuable aspects of glow squids lies in their natural ability to produce light through bioluminescence—a chemical reaction involving luciferin and luciferase enzymes. This trait has made them a key subject in marine biology, neuroscience, and environmental science research.

Scientists study glow squids to understand:

• How deep-sea organisms adapt to extreme pressure, darkness, and cold.
• Mechanisms of intraspecies communication and camouflage in low-light environments.
• Predator-prey dynamics, including counter-illumination strategies that help squids blend into ambient light from above.
• Biochemical pathways behind light production, which may inspire advancements in medical imaging, biosensors, and sustainable lighting technologies.

Because glow squids are typically studied in controlled marine labs or observed via submersibles, their use in research is considered relatively sustainable and non-invasive, contributing to broader ocean conservation efforts.

Aquarium Trade and Display Applications

Glow squids, particularly species like the luminous Loligo and other bioluminescent cephalopods, are highly sought after in the aquarium trade. Their mesmerizing light displays make them ideal centerpieces for public aquariums and specialized private collections aiming to replicate deep-sea ecosystems.

Key considerations for keeping glow squids in captivity include:

• Dark, temperature-controlled tanks that mimic deep-ocean conditions.
• Low-stress environments with minimal handling and disturbances.
• Specialized lighting systems that allow observation without disrupting natural behaviors.
• Expert care due to their short lifespans and sensitivity to water chemistry.

While not common in standard home aquariums, institutions like marine science centers and large public aquariums often feature live glow squids in nocturnal or deep-sea exhibits, educating the public about bioluminescence and ocean biodiversity.

Traditional Medicine: Beliefs vs. Evidence

In certain cultures, particularly in parts of East and Southeast Asia, glow squids and other cephalopods are used in traditional medicine systems. They are believed to possess properties that can:

• Improve blood circulation
• Boost energy and stamina
• Support liver function
• Enhance vitality in aging individuals

These applications often involve drying the squid, grinding it into powder, or boiling it into tonics. However, there is no clinical or scientific evidence supporting these health claims. Regulatory bodies such as the World Health Organization (WHO) and the U.S. Food and Drug Administration (FDA) do not recognize glow squid as a medicinal substance.

Consumers should exercise caution when using glow squid or any marine animal for therapeutic purposes, as contamination, allergic reactions, or interactions with existing medications may pose health risks.

Use Case	Primary Benefit	Scientific Validity
Culinary Preparation	Versatile ingredient with unique texture and visual appeal	High – widely accepted in gastronomy
Bioluminescence Research	Insights into marine adaptation and biochemical processes	High – peer-reviewed and actively studied
Aquarium Exhibits	Educational and aesthetic value in marine displays	Medium – limited to specialized facilities
Traditional Medicine	Cultural significance and anecdotal health claims	Low – no proven therapeutic effects

Important Note: While glow squids offer exciting possibilities across multiple domains, consumers and researchers alike should rely on verified information and sustainable practices. In culinary use, ensure proper sourcing and freshness. In scientific or aquarium settings, prioritize ethical treatment and habitat replication. For medicinal claims, consult healthcare professionals and avoid substituting unproven remedies for evidence-based treatments.

Benefits of Glow Squid

Glow squids, known for their mesmerizing bioluminescent abilities, are not only a marvel of marine biology but also a valuable resource across culinary, nutritional, scientific, and educational domains. While no scientific studies have confirmed direct health benefits from consuming glow squids, their unique properties and sustainable availability make them an increasingly important species in both gastronomy and research.

Culinary Versatility

Glow squids are prized in global cuisines for their tender texture and mild, slightly sweet flavor. When properly cooked, they remain soft and succulent—overcooking is the primary cause of toughness, so precise preparation is key.

• Commonly featured in Mediterranean dishes like grilled calamari, stuffed squid, and seafood stews
• Widely used in Asian cuisine for stir-fries, sushi, sashimi, and noodle dishes
• Perfect for marinating due to their neutral taste, absorbing flavors from garlic, lemon, soy sauce, and herbs
• Ink is used to create visually striking and flavorful dishes such as squid ink pasta and risotto

Pro tip: Quick searing or slow braising yields the best texture—avoid medium cooking times that toughen the meat.

Nutritional Advantages

Glow squids offer a nutrient-dense, low-calorie seafood option ideal for health-conscious diets. They are rich in high-quality protein and essential micronutrients vital for overall wellness.

• Excellent source of lean protein (about 15–20g per 3-ounce serving)
• Rich in omega-3 fatty acids, which support cardiovascular health and cognitive function
• Contains vital vitamins such as B12 (for nerve function) and selenium (a powerful antioxidant)
• Low in saturated fat and calories, making it suitable for weight management plans

Health insight: Regular consumption of omega-3-rich seafood may reduce inflammation and lower risk of chronic diseases.

Scientific and Biotechnological Significance

The natural bioluminescence of glow squids has made them a focal point in marine science and biotechnology research. Their light-producing mechanisms offer insights into cellular communication, predator-prey dynamics, and deep-sea adaptation.

• Studied for luciferase enzymes and photoprotein systems that could inspire new imaging technologies in medicine
• Used in ecological monitoring to understand ocean health and species migration patterns
• Contribute to evolutionary biology by revealing how organisms adapt to extreme environments
• Potential applications in developing bio-sensors and non-invasive diagnostic tools

Research highlight: Bioluminescent proteins from squids are being engineered for use in real-time tracking of cancer cells.

Sustainability and Ethical Sourcing

Glow squid populations are generally resilient and reproduce rapidly, making them a more sustainable seafood choice compared to overfished species. Responsible fishing practices further enhance their environmental profile.

• Many fisheries adhere to quotas and seasonal restrictions to prevent overharvesting
• Typically caught using selective jigs or traps that minimize bycatch and seabed damage
• Supports livelihoods of small-scale fishers in coastal communities
• Choosing certified sustainable squid helps promote ocean conservation and ethical supply chains

Eco-conscious choice: Look for MSC or ASC certifications when purchasing glow squid products.

Educational and Aesthetic Value

Glow squids captivate audiences in public aquariums and educational institutions, serving as ambassadors for marine biodiversity and ocean conservation.

• Used in live exhibits to demonstrate bioluminescence and deep-sea adaptations
• Featured in school programs to teach students about marine ecosystems and animal behavior
• Inspire interest in STEM fields through interactive displays and research collaborations
• Photogenic nature makes them popular subjects in documentaries and underwater photography

Engagement tip: Interactive touch tanks and augmented reality displays enhance visitor learning experiences.

Environmental and Conservation Impact

Beyond their intrinsic value, glow squids play a role in broader marine conservation efforts by highlighting the importance of protecting deep-sea habitats and maintaining ecosystem balance.

• Act as indicator species for changes in ocean temperature and acidity
• Support food webs as both predators and prey in mid-water ecosystems
• Research on their migration helps inform marine protected area design
• Raise public awareness about light pollution and its effects on nocturnal marine life

Conservation note: Protecting squid habitats contributes to the resilience of entire oceanic ecosystems.

Expert Insight: While glow squids do not provide direct medicinal benefits, their combination of nutritional quality, sustainability, and scientific value makes them a highly beneficial species. Encourage consumers to appreciate them not just as food, but as a gateway to understanding marine innovation and environmental stewardship.

Benefit Category	Key Attributes	Real-World Applications	Sustainability Rating
Culinary Use	Tender texture, mild flavor, versatile preparation	Calamari, sushi, pasta, grilling, stir-fry	★★★★☆
Nutritional Value	High protein, omega-3s, low fat, rich in B12 and selenium	Heart-healthy diets, weight management, brain nutrition	★★★★★
Scientific Research	Bioluminescence, enzyme systems, deep-sea adaptation	Medical imaging, bioengineering, ecology studies	★★★★★
Educational Use	Visual appeal, interactive learning potential	Aquarium exhibits, school curricula, documentaries	★★★★☆
Environmental Impact	Indicator species, low bycatch, rapid reproduction	Sustainable fisheries, marine conservation, policy planning	★★★★☆

Additional Considerations

• Allergen Awareness: Squid is a mollusk and may trigger shellfish allergies—always label clearly in food service settings
• Cooking Techniques: Tenderize with milk or enzymatic marinades (like pineapple juice) for enhanced texture
• Storage Tips: Fresh glow squid should be consumed within 1–2 days or frozen promptly to preserve quality
• Ethical Labeling: Promote transparency by sharing origin, catch method, and sustainability certifications
• Future Potential: Ongoing research into squid-derived biomaterials may lead to breakthroughs in biodegradable electronics and medical devices

How to Store Glow Squid: A Complete Guide to Freshness and Safety

Proper storage of glow squid is essential to preserve its delicate texture, vibrant appearance, and rich flavor. As a highly perishable seafood, glow squid begins to degrade quickly after harvest if not handled correctly. Whether you're working with live, fresh, cooked, or preserved squid, the right storage method ensures food safety, prevents spoilage, and maintains culinary quality. This guide covers best practices for storing glow squid in all forms, from immediate use to long-term preservation.

Important Note: Glow squid, like all cephalopods, is extremely sensitive to temperature and handling. Always use clean utensils and containers, and avoid cross-contamination with raw meats or other seafood to prevent bacterial growth and maintain freshness.

Storing Live Glow Squid

Due to their deep-sea habitat and specialized environmental needs, live glow squids are rarely available outside of research facilities or specialized aquaculture settings. Unlike bivalves such as oysters or clams, they cannot survive for extended periods out of their natural environment.

If you do obtain live glow squid—such as through a deep-sea fishing expedition or marine supplier—it’s critical to process them as quickly as possible to ensure optimal freshness and humane treatment.

• Keep live squid in a cool, dark container with circulating, well-oxygenated seawater at approximately 40°F (4°C)
• Use an aerated aquarium system if transporting for a few hours
• Avoid overcrowding, as stress accelerates deterioration
• Do not store live squid for more than 4–6 hours; prolonged captivity leads to muscle breakdown and loss of bioluminescent properties
• Process immediately after capture to preserve texture and flavor

Expert Tip: If you're using live glow squid for culinary purposes, dispatch them humanely and clean them promptly. This minimizes enzyme activity that can cause rapid softening of the flesh.

Storing Fresh Glow Squid

Fresh glow squid is best enjoyed within hours of harvest, especially for raw preparations like sushi, sashimi, or crudo. However, short-term refrigeration is possible with proper handling.

• Immediate Use: Use fresh glow squid the same day for peak quality, particularly in raw dishes.
• Short-Term Refrigeration: Clean and gut the squid thoroughly, then place in a sealed, airtight container. Store on a bed of crushed ice in the coldest part of the refrigerator (32°F–40°F / 0°C–4°C). Consume within 1–2 days.
• Long-Term Freezing: For extended storage:
  • Clean, gut, and portion the squid
  • Vacuum-seal or wrap tightly in plastic wrap and aluminum foil to prevent freezer burn
  • Label with the date and freeze at 0°F (-18°C) or lower
  • Use within 3–6 months for best texture and flavor
• Storing Squid Ink: Glow squid ink can be collected during cleaning and stored separately. Place in a small, airtight container or ice cube tray, freeze, and use later in dishes like squid ink pasta, risotto, or sauces.

Storing Cooked Glow Squid

Cooked glow squid should be cooled quickly and stored properly to prevent bacterial growth and texture degradation. Overcooking can make squid rubbery, so gentle reheating is key.

• Allow cooked squid to cool to room temperature (no more than 2 hours)
• Transfer to an airtight container and refrigerate at or below 40°F (4°C)
• Consume within 1–2 days for best quality
• For longer storage, freeze cooked squid:
  • Portion into meal-sized servings
  • Use vacuum-sealed bags or freezer-safe containers
  • Store at 0°F (-18°C); use within 2–3 months
• Thawing: Always thaw frozen cooked squid in the refrigerator overnight. Reheat gently using steam, a sauce, or brief sautéing to avoid toughness.

Dried or Preserved Glow Squid

In many coastal and island cultures, glow squid is preserved through drying, salting, or fermentation to extend shelf life and enhance umami flavor. These methods are excellent for long-term storage and specialty cooking.

• Dried Glow Squid:
  • Air-dry cleaned squid in a cool, shaded, well-ventilated area or use a food dehydrator
  • Store in an airtight container away from moisture and light
  • Shelf life: Up to 1 year when properly dried and stored
  • Rehydrate by soaking in warm water for 20–30 minutes before use in stir-fries, soups, or salads
• Salted Glow Squid:
  • Cover cleaned squid in coarse sea salt for 12–24 hours to draw out moisture
  • Rinse thoroughly under cold water before cooking to remove excess salt
  • Store salted squid in the refrigerator for up to 2–3 weeks
  • For longer storage, vacuum-seal and freeze for up to 6 months

Storage Type	Temperature	Shelf Life	Best Practices
Live Glow Squid	35–40°F (2–4°C) with seawater	4–6 hours	Use aerated container; process quickly
Fresh (Refrigerated)	32–40°F (0–4°C)	1–2 days	Store on ice in sealed container
Fresh (Frozen)	0°F (-18°C) or lower	3–6 months	Vacuum-seal; label with date
Cooked (Refrigerated)	≤40°F (4°C)	1–2 days	Cool quickly; use airtight container
Cooked (Frozen)	0°F (-18°C)	2–3 months	Thaw in fridge; reheat gently
Dried	Cool, dry place	Up to 1 year	Store airtight; rehydrate before use
Salted	Refrigerated or frozen	2–3 weeks (fridge), 6 months (frozen)	Rinse before cooking; vacuum-seal for freezing

Key Handling and Storage Tips

• Always handle glow squid with clean hands, gloves, and sanitized tools to prevent contamination
• Prevent cross-contamination by storing squid away from raw meats and ready-to-eat foods
• Use moisture-resistant packaging to avoid freezer burn and dehydration
• Avoid strong-smelling foods in the refrigerator, as squid can absorb odors easily
• Label all stored squid with the date and type (raw, cooked, etc.) for easy tracking
• Inspect before use—discard if there’s a sour smell, slimy texture, or discoloration

Culinary Insight: Glow squid’s bioluminescence may fade after storage, but its flavor and texture remain excellent when handled properly. Use frozen or preserved squid in richly flavored dishes like stews, curries, or pasta where appearance is less critical than taste.

By following these detailed storage guidelines, you can maximize the shelf life and quality of glow squid in any form. Whether you're a chef, seafood enthusiast, or home cook, proper handling ensures a safe, delicious, and sustainable experience with this unique and fascinating marine delicacy.

Frequently Asked Questions About Glow Squids

Q1: Can glow squids be eaten safely?

Yes, glow squids are safe to eat when properly handled and cooked. They are a popular seafood delicacy enjoyed in many coastal regions and international cuisines, including Japanese, Korean, and Mediterranean dishes. As with any seafood, freshness and proper preparation are key to ensuring food safety. Glow squids should be cleaned thoroughly to remove inedible parts and cooked to an internal temperature of at least 145°F (63°C) to eliminate potential pathogens. Avoid consuming raw or undercooked glow squid unless it has been previously frozen to kill parasites, as recommended by food safety guidelines.

Q2: What do glow squids taste like?

Glow squids have a delicate, slightly sweet flavor that is often described as a cross between shrimp and scallops. Their texture is tender and chewy when cooked correctly—overcooking can lead to a rubbery consistency, so timing is crucial. The mild taste makes them highly versatile in cooking, absorbing marinades and seasonings well. Whether grilled, sautéed, boiled, or served in soups and stir-fries, glow squids offer a satisfying umami-rich experience that appeals to both seafood enthusiasts and adventurous eaters.

Q3: Are glow squids good for health?

Yes, glow squids are a highly nutritious seafood option with several health benefits:

• High-Quality Protein: A 3-ounce (85g) serving provides about 16–18 grams of protein, supporting muscle growth and repair.
• Low in Calories: With only around 75–85 calories per serving, they are ideal for weight-conscious diets.
• Rich in Omega-3 Fatty Acids: These essential fats support heart and brain health and help reduce inflammation.
• Vitamins and Minerals: Glow squids are an excellent source of vitamin B12, selenium, copper, phosphorus, and iron—nutrients vital for energy production, immune function, and red blood cell formation.
• Low Mercury Content: Compared to larger predatory fish, glow squids accumulate minimal mercury, making them a safer choice for regular consumption.

Incorporating glow squids into a balanced diet can contribute to improved cardiovascular health, cognitive function, and overall nutrient intake.

Q4: What is the lifespan of a glow squid?

Glow squids typically live between 1 to 2 years, depending on the species and environmental factors such as water temperature, predation pressure, and food availability. Most glow squid species are fast-growing and reach maturity within a few months. After spawning, many individuals die shortly afterward—a common trait among cephalopods known as semelparity (reproducing once and then dying). Their relatively short lifespan is offset by high reproductive rates, ensuring population sustainability in deep-sea and coastal ecosystems.

Q5: Do glow squids glow in the dark?

While glow squids do not emit a constant glow like a light bulb, they possess specialized bioluminescent organs called photophores that allow them to produce light through chemical reactions involving luciferin and luciferase enzymes. This ability is primarily used in deep ocean environments for:

• Camouflage: Counter-illumination helps them match downwelling light from above, making them less visible to predators below.
• Communication: Flashing patterns may be used to signal other squids during mating or social interactions.
• Prey Attraction: Some species use light to lure small fish or planktonic organisms.
• Distraction: They can release bioluminescent ink to confuse predators and escape.

Their glowing capability is a remarkable adaptation to life in the deep sea, where sunlight does not penetrate, and visibility is extremely limited.