Photo by Klaus Jost
To Do Today:
- PT – Cardio – Bike/Row/Swim for 45-60 min at low to moderate intensity // Strength – Arm group // Abs
- Review historical shark attack statistics Here. Consider a donation to the Global Shark Attack File.
Dangerous Marine Life
When you find yourself treading water, at sea, towards the end of the day (or any time of day considering your luck) you may see many types of marine life around you; some more dangerous than others. Generally, sharks are your greatest danger, followed by barracudas. However, most marine life will not deliberately attack a human.
The most common injuries from marine life are wounds from bites, stings, or punctures from sea life that get less TV/movie time. With the exception of sharks and barracudas, most injuries are a result of either trying to catch game or from contact abrasion with marine life.
Injuries from encounters with dangerous marine life are generally sustained in one of the following way:
- Accidentally brushing past a venomous sessile or floating organism when swimming
- Entering waters frequented by dangerous jellyfish (e.g., box jellyfish)
- Inadvertently treading on a stingray, weeverfish or sea urchin
- Unnecessary handling of venomous organisms
- Invading the territory of large animals when swimming or at the waterside
- Swimming in waters used as hunting grounds by large predators; or
- Intentionally interfering with, or provoking, dangerous sea life.
Apex predator. Only about 20 percent of all shark species are known to attack people. Sharks have an acute sense of smell, and the smell of blood in the water will draw them to their prey. They are also very sensitive to any abnormal vibrations in the water; therefore, the sound caused by a struggling swimmer or surface/underwater explosions will attract them.
Species of dangerous sharks:
- The great white shark (Carcharodon carcharias) lives mainly in the open ocean, although some swim into shallow water. Most of the attacks on people have happened in estuaries. The great white shark is responsible for the largest number of reported attacks on humans. It is thought that humans might be mistaken for its normal seal prey.
- The tiger shark (Galeocerdo cuvier) is extremely widespread in the tropics and subtropics. Following the great white shark, the second most reported attacks on humans are attributed to tiger sharks.
- The mako shark (Isurus oxyrinchus) is mainly an open ocean shark and occurs in all temperate and tropical oceans. It is often aggressive and dangerous when close to shore.
- The smooth hammerhead shark (Sphyrna zygaena), with its very distinctive head shape, lives in all warm water oceans.
- The silvertip shark (Carcharhinus albimarginatus) is very abundant around reefs and islands in the Pacific and Indian oceans.
- The bull shark (Carcharhinus leucas) is mainly located in the warm oceans of the world, although it can at times be found up the Amazon and rivers in Australia, Central America and south-eastern Africa (Halstead et al., 1990).
The shark skeleton is made from cartilage rather than bone. This cartilage makes sharks very flexible, allowing them to twist 360 degrees and whirl around and bite an unsuspecting swimmer. Sharks also don’t have an air bladder and if they stop swimming they will sink. To overcome this disadvantage, they have very large oil-filled livers giving them some buoyancy. An advantage of not having a swim bladder is vertical mobility allowing sharks to rapidly move upward in the water column without the development of bends. In addition, their pectoral fins act as glide-planes and provide great lift as the shark swims.
Sharks possess electroreception with a system of jelly-filled pores around the head and mouth that can detect small electric fields of less than 0.01 microvolt. Sharks can also see color, as indicated by the presence of cone cells in their retinas and, similar to cats, they have a light-reflecting layer to enhance their night vision. This is important to swimmers to realize that swimming and diving in shark infested waters at night is more dangerous.
Categories of Shark Attacks:
- Provoked attacks are caused by humans touching sharks. Often this involves unhooking sharks or removing them from fishing nets. However, recently there have been a number of incidents involving divers who were attacked after grabbing or feeding a shark while underwater.
- Unprovoked attacks happen when sharks make the first contact. This can take three forms:
Hit-and-Run Attacks happen near beaches, where sharks hunt fish. In pounding surf, strong currents, and murky water, a shark may mistake the movements of humans, usually at the surface, for those of their normal fish-food. The shark makes one grab, lets go, and immediately leaves the area. Legs or feet are often bitten; injuries usually are minor and deaths rarely occur.
Sneak Attacks take place in deeper waters. The victim doesn’t see the shark before the attack. The result can be serious injury or death, especially if the shark continues to attack.
Bump-and-Bite Attacks happen when the shark circles and actually bumps the victim with its head or body before biting. As in the sneak attack, the shark may attack repeatedly and cause serious injury or death.
There are different modes of shark attacks and investigations that sharks go through when they come across humans. The following list shows what a shark can do when it comes across a human.
- Indifference (rare)
- Approach with swift visual inspection from a distance without follow-up
- Approach with surveillance circling – without follow up or follow-up, contact and attack
- Approach with brush-past, without follow-up (wounding possible)
- Charge with collision (upwards trajectory generally)
- Charge with single or double investigative bite without tearing
- Charge with biting and removal of flesh (death in 45% of cases)
- Multiple feeding-frenzy charge (death in 100% of cases)
Sharks do not attack humans for the sole purpose of hunger. Sharks do not know what the feeling of hunger is, and in fact, can go for many months without eating. This is not to say that sharks do not attack with the intention of seeking prey. Many attacks on divers and surfers especially can be attributed to searching for food. To a shark, a surfer on a surfboard resembles that of a seal or sea lion, or a diver in a black wetsuit can look like other prey.
Sharks also attack humans because they have been provoked or agitated by the person. Many spear-fishers have been attacked by reef sharks because when they spear fish, the blood from the fish and it’s vibrations can sometimes result in a feeding frenzy by many sharks. Bright colors can also contribute to reasons for attack. Sharks see color, and have very good eyesight. Orange and yellow seem to aggravate some species of shark, and lead to attacks.
When most sharks attack, the first bite is usually a “tester.” Like most people, when sampling food, they bite once, revel in the taste, and then decide whether or not to continue… with most sharks, sampling occurs as well. The trouble is, with the sampling of a Great White or other larger predatory sharks, the first bite is so massive or severe that many people die from their injuries, and do not actually die from being consumed. A lot of fatalities can be attributed to people bleeding to death or dying from shock.
Preventing shark attacks:
The following is a list of preventative measures that may reduce the possibility of shark attack:
- Do not touch, tease, or entice sharks.
- If you cut or injure yourself, get out of the water if possible. Do not stay in the water with blood around you. Sharks can smell blood from over a mile away. Woman during menstruation are at particular risk. Try to move away from deceased casualties.
- Watch other fish and turtles in the area. If they start acting erratic, be alert that a shark might be in the area.
- Do not swim in waters that have been deemed dangerous. Avoid swimming in murky waters. If you feel something brush up against you…. get out of the water to check to make sure that you have not been bitten. Many shark attack victims have noted the lack of pain from being bitten. If you have been brushed against by something, get out and investigate.
- If you don’t feel right in the water get out. Nothing can be said for “gut feeling.”
- Steer clear of dolphins and seabirds. They may not only attract sharks, but also often seek the same prey.
- Skip swimming after heavy rains, which may move some freshwater fish, including sharks, into areas they would not otherwise frequent.
- Sharks sometimes get stuck in lagoons and small bays during low tide, so be careful when swimming in such areas at these times.
- Avoid diving from boats but, if you must, refrain from doing so at night and be sure to carefully scan the surrounding water beforehand.
- Some sharks are very small and resemble tropical fish. Avoid touching fish around you, as you could find your hand in a tiny, yet well-toothed, mouth.
- Pay attention to fish swimming patterns. If fish start to school or dart away, chances are a shark or other potential predator is nearby.
- Fishing boats and anglers from shore can attract sharks looking for an easy seafood meal, so refrain from swimming near them.
- The splash of a dog paddling is like a dinner bell for sharks. Do not take your pet with you in waters where there is even a remote chance of encountering a shark.
- Splashing and other erratic movements signal distress and can alert sharks to your presence. Try to keep strokes and kicks smooth and even.
- Got an uneven tan? Avoid swimming in open water because skin color contrasts seem to attract sharks, resembling color variations found on fish.
- Brightly colored swimwear, colorful surfboards and shiny jewelry mimic natural fish bling.
- Mouths of rivers, channels, deep drops and areas between sandbars tend to attract sharks. Skip swimming in these places, as well as far from shore.
- Avoid swimming in dirty, murky water. It can impair your field of vision and that of sharks, too, increasing the chances of an encounter.
- Sharks are creatures of habit. Do not swim in areas where a shark attack has recently occurred, since the same shark, or others, may still frequent the spot.
- Try to swim on sunny, clear days. Foggy mornings and dusk may cause a shark to confuse you with prey.
- Don’t swim in waters known to be frequented by sharks. Consult with lifeguards and other authorities for more specific regional information.
- Swim in a group or at least be sure to have a partner with you. Sharks most often attack lone individuals.
- Stay alert as to what is going on in the surrounding water environment.
- Avoid looking like a seal. Reclining on a surfboard and wearing a wetsuit and fins can give you a seal’s silhouette from a shark’s perspective below.
- Think like a shark. If you see lots of fish or seals, chances are that sharks could be around and could confuse you with dinner.
- Don’t wander too far from shore. Doing so isolates you and places you away from assistance.
- Avoid the water at night, dawn, or dusk. Many sharks are most active at these times and are better able to find you than you are to see them.
- Don’t go into waters containing sewage. Sewage attracts bait fishes, which in turn attract sharks.
- Avoid waters being fished and those with lots of bait fishes. Diving seabirds are good indicators of such activities.
- Don’t enter the water if sharks are present. Leave immediately if possible if sharks are seen.
- Avoid an uneven tan and brightly colored clothing. Sharks see contrast particularly well, so use extra caution when waters are cloudy.
- Don’t splash a lot. Also, keep pets out of the water. Erratic movements can attract sharks.
- Use care near sandbars or steep drop-offs. These are favorite hangouts for sharks.
- Don’t relax just because porpoises are nearby. Sightings of porpoises do not indicate the absence of sharks. Both often eat the same foods.
- If attacked by a shark, the general rule is “Do whatever it takes to get away” Some people have successfully chosen to be aggressive, others passive. Some yelled underwater, others blew bubbles. Go down fighting.
Predator. The barracuda is any of about 20 species of predatory fishes of the family Sphyraenidae (order Perciformes). Barracudas are usually found in warm, tropical regions; some also in more temperate areas. They are swift and powerful, small scaled, slender in form, with two well-separated dorsal fins, a jutting lower jaw, and a large mouth with many sharp large teeth. Size varies from rather small to as large as 4-6 feet (1.2-1.8 meters) in the great barracuda (Sphyraena barracuda) of the Atlantic, Caribbean, and the Pacific.
Barracudas are bold and inquisitive, and fearsome fishes, that are dangerous to humans. The great barracuda is known to have been involved in attacks on swimmers. In Hawaii, they have been known to inhabit open waters and bay areas in the shadows, under floating objects. To avoid them, don’t wear shiny objects. They are attracted to shiny, reflective things that look like dinner. They cause harm with their sharp jagged teeth and strong tearing jaws; slashing and creating jagged tears in your skin.
A group of swimmers can maintain a 360 degree watch while in the water to protect against sharks and barracudas. A group can frighten away or fight off sharks/barracudas better than one person can. Keep all clothing on, including footwear. Historically, sharks/barracuda attack unclothed individuals in groups first, mainly the feet. Clothing also protects you against abrasions from a shark’s tough skin should the shark brush up against you. Avoid urinating heavily, let urine dissipate between discharges. If you must defecate, do so in small amounts and toss it as far away from the group as possible. Do the same if you must vomit.
If attacked, the use of firearms by swim sentries should be used with extreme caution because of the risk of injury to other swimmers. If unarmed or unable to make an improvised weapon, kick and strike the shark. Avoid using your bare hands to strike the shark, injury can result to your hands due to a shark’s tough skin. Target areas on a shark are the gills, eyes, and underbelly. Blows to the snout are also not recommended because a shark will tilt its head up and thrust its jaws forward when biting.
A number of swimmers have been bitten by moray eels, their sharp teeth designed to lock on to prey sometimes causing severe damage. These eels are not, by nature, aggressive towards people but can attack if provoked. Many attacks can be blamed on the foolish practice of fish feeding by hand. Accustomed to receiving handouts, some approach divers on sight and can bite a hand which they believe to be holding food.
The Nassau grouper is common resident in the waters off the Gulf of Mexico and the Caribbean. Some divers have been “bitten” by over friendly Nassau groupers that are used to human interaction in popular dive feeding sites. During feedings groupers occasionally will take the entire fist and forearm of unsuspecting diver into their large mouths. Grouper have several sets of teeth, placed in the mouth to act as raspers or holding teeth. The fish gulps down its prey using these raspers to prevent the smaller fish from escaping. The teeth are not used to tear or slash, as with barracuda or sharks. One can imagine the problem with this when considering that some of these fish grow to be as large as 800 pounds. These bites primarily result in loss of skin from the back of the hand and fingers, often followed by a severe infection.
Crocodiles are found in tropical areas of Africa, Asia, the western Pacific islands and the Americas. The majority of species live in fresh water. The largest living crocodiles may exceed 7.5 m in length. Crocodiles normally hunt at night and bask during the day, but might also hunt during the day if food is in short supply. All crocodiles are capable of inflicting severe harm or causing death to humans. The more dense their populations, the more dangerous are individual crocodiles. The saltwater crocodile (Crocodylus porosus) of south-eastern Asia is probably the most dangerous of all the marine animals. It lives mainly in mangrove swamps, river mouths and brackish water inlets, but has been seen swimming far offshore. The Nile crocodile (C. niloticus) has been rated as second only to the saltwater crocodile in danger to humans.
There are only two species of alligator: the Chinese alligator (Alligator sinensis) and the American alligator (A. mississipiensis). The Chinese alligator, found in the Yangtze River basin of China, is quite small (<2.5 m) and timid and is not considered to be a significant threat to humans. The American alligator, which lives in freshwater swamps and lakes in the south-eastern USA, is larger (up to 6 m in length) and potentially dangerous to humans. Attacks occur infrequently.
The hippopotamus (Hippopotamus amphibious) is an aquatic mammal chiefly inhabiting freshwater rivers and lakes from the Upper Nile down to South Africa. Despite being a herbivore, the hippopotamus is responsible for a significant number of human deaths in Africa. Due to their sudden and violent nature and ability to swim quickly, hippopotami pose a serious threat to humans in the water. They are generally peaceable creatures, and most often a herd will scatter, or at least submerge, at the approach of humans, but attacks are not uncommon. The majority of incidents are due to ignorance of their habits, in particular moving between a group of hippopotami on shore and water.
Seals and sea lions
Seals and sea lions are not aggressive towards humans under normal circumstances. During the mating season, however, or when with pups, bulls might turn aggressive and attack intruders. Of particular concern are the Californian sea lion (Zalophus californianus), found along the west coast of North America and the Galapagos, and the bearded seal (Erignathus barbatus), found on the edge of the ice along the coasts and islands of North America and northern Eurasia.
Piranhas are restricted to the fresh waters of northern South America, in the Amazon Basin. The largest species is Pygocentrus piraya, which reaches a size of 60 cm. Piranhas have powerful jaws with very sharp teeth, which they use to communally attack and kill large prey animals. They can be dangerous to humans. Splashing of the surface water is sufficient to attract a school of piranhas.
Catfish (freshwater and marine)
Catfish are bottom dwellers living in marine, freshwater or estuarine environments. They possess venomous dorsal spines, which can inflict painful wounds even when the fish is dead. The majority of catfish stings result from handling catfish while sorting fish catches. Some species, such as Heteropneustes fossilis from India, have been known to actively attack humans, leaving a painful sting. Be extremely careful when handling and sorting catfish.
Stingray (freshwater and marine)
Stingrays are found in the Atlantic, Indian and Pacific oceans. They are predominantly marine, but the South American river ray (Pontamotrygonidae) lives in fresh water. Stingrays tend to be partially buried on sandy or silty bottoms in shallow inshore waters. Up to six venomous spines in their tails can stab unwary swimmers who happen to tread on or unduly disturb them. All stingray wounds, no matter how minor, should receive medical attention to avoid the risk of secondary infection. Some injuries caused by venomous stingrays can be fatal for humans if the spine pierces the victim’s trunk; deaths have been reported for both marine and freshwater species. Always “shuffle” feet when walking along sandy lagoons or shallower waters where stingrays frequent.
Scorpionfish (estuarine and marine)
All species of scorpionfish possess a highly developed venom apparatus and should therefore be treated with respect. The estuarine stonefish (Synanceia horrida , syn. S.trachynis) is the most venomous scorpionfish known and occurs throughout the Indo-Pacific. The reef stonefish (Synanceia verrucosa) resembles coral rubble and lies motionless in coral crevices, under rocks, in holes or buried in sand or mud, where divers often mistake it for a rock. The pain associated with stings by a stonefish is immediate and excruciating and can last for days (Williamson et al., 1996). The lionfish and true scorpionfish are also venomous. Deaths have been attributed to stone-fish but are very difficult to confirm
Weeverfish are confined to the north-eastern Atlantic and Mediterranean coasts. All four species (Trachinus spp. and Echiichthyssp.) contain venomous dorsal and gill cover spines. They are small (less than 4.5 cm) and lie partly buried in sandy bays at extreme low water where swimmers and beach walkers frequently step on them. Weeverfish are regarded by some as the most venomous fish found in temperate European water
Surgeonfish are herbivorous reef dwellers equipped with a sharp, moveable spine on the side and base of the tail. When excited, the fish can direct the spine forward, making a right angle with the body, ready to attack. Large surgeonfish, such as the Achilles surgeonfish (Acanthurus achilles) and the blue tang (Acanthurus coeruleus) of the warm seas of the western Atlantic, use their spines in defence and cause deep and painful wounds with a quick lashing movement of the tail.
Snakes (freshwater and marine)
Poisonous snakes are air-breathing, front-fanged venomous reptiles, and many are associated with both the marine and freshwater environments. Of the 50 species of sea snake, the majority live close inshore or around coral reefs. They appear similar to land snakes, but have a flattened tail to aid in swimming. They are curious, generally non-aggressive creatures, but can be easily provoked to attack. All sea snakes are venomous and can inflict considerable harm if disturbed.
Of the freshwater aquatic snakes, possibly the water moccasin or cottonmouth (Agkistrodon piscivorus) is the most dangerous to humans, the venom attacking the nervous and blood circulatory systems of the victim. The water moccasin is a pit-viper found throughout the south-eastern part of the USA. The species is never far from water and swims with its head well above the surface. When threatened, the snake opens its mouth wide to reveal the almost white lining, which gives it its common name. The species can be aggressive and is densely populated in some areas. Its bite can result in gross tissue damage, with amputations of the affected limb not uncommon. Other species of the genus Agkistrodon are found throughout North America and south-eastern Europe and Asia.
Some non-venomous but large freshwater snakes such as the semi-aquatic anaconda (Eunectes murinus) can present a danger. The anaconda, which reaches lengths of up to 7.6 m, lives in tropical South America. Anacondas generally constrict and suffocate large prey, often viciously (non-venomous) biting the victim before coiling. Attacks on humans have occurred, but the snake is not generally aggressive towards people and will usually endeavor to escape if approached.
Coral, dead or alive, can inflict painful cuts. Clean all coral cuts thoroughly. DO NOT use iodine to disinfect any coral cuts. Some coral polyps feed on iodine and may grow inside the flesh.
Jellyfish, Portuguese Man-of-War, Anemones, and Others
This group of marine animals inflicts injury by stinging their victims with their tentacles. Contact with their tentacles produces burning pain, a rash, and small hemorrhages on the skin. Shock, muscular cramping, nausea, vomiting, and respiratory distress may also occur. Gently remove the clinging tentacles with a towel and wash or treat the area. Use diluted ammonia or alcohol and talcum powder to treat the injury if available.
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