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Dangerous Sea Life
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by Jean-Philippe Soule
There are about 350 species of sharks, only 30 species could potentially be dangerous to humans and only 12 are reported potentially aggressive and dangerous. To put things in perspective 300 times more drowning are reported than fatal shark attacks.
Among the most dangerous to humans are:
- Great white
- Tiger shark
- Bull shark
- Oceanic White tip
- Gray sharks (territorial?)
Only a few species consider people as prey. They usually attack mistaking humans for marine animals on which they feed (mammals or sea turtles).
Most of the other sharks attack are provoked (feeding, spearfishing, bleeding, etc.)
Sharks dont have many predators. They might shy away if charged by a person, or be wary of someone facing them with a stick or long object. In other situations, some species of sharks have been known to attack at great speed without any warning.
Sharks weak points are their gills (striking them there with the handle of a knife or a snorkel could fend them off)
For more information about sharks we invite you to follow this link to our special section on sharks written by Marine Biologist Wade Smith.
Also read Scary Shark Encounter by Jean-Philippe Soule
Large carnivorous fish (up to 7 feet). Can be found in large schools.
Doesnt feed on humans, but have reported to accidentally attack people wearing brightly colored things (watch, necklace, dive lights (especially at night), etc.
Depending on geographical locations, some species seem to show more or less aggressiveness.
Crocodiles, Alligators and Caimans
Very aggressive, fast and powerful. They are territorial highly dangerous to humans. Feeding usually happens in the evening. Large crocodiles have been reported to attack canoes. Salt water crocodiles living in river estuaries are known to be generally bigger and more aggressive toward people. They can sometimes also be found up rivers in fresh water. They can also attack on land and run extremely fast.
In case of confrontation, humans dont have much chance but poking the eyes (with a stick for example) has been reported as the thing to try.
Sea lions are usually playful, however they can be territorial and dangerous especially during the mating seasons. Accidents among divers are reported much more frequently than with sharks. Advice: get out of water if sea lions show territorial behavior (barking), dont swim with large males, dont approach sea lions during the mating season.
Scary looking, they can reach 6 to 8 feet. Their teeth are razor sharp and their bites can lead to profuse bleeding and often get infected. Usually moray eels arent aggressive toward divers. They even sometimes get fed. But sometimes they can be territorial or become aggressive and go after speared fish. Read: Jean-Philippes bad encounter with a moray eel.
Moray eels can be toxic to eat (the gymnothorax toxin resemble the ciguatera poisoning)
Octopus and squids
Octopus can grow quite big and do not usually attack people but there have been a few recorded incidents with divers. Mainly playing or defending themselves. Octopus have a beak and can inject a mild venom (* the small blue ring octopus venom can be deadly).
Large squids have been reported to be extremely aggressive and injure fisherman. Giant Squids live deep in the ocean (few thousand feet deep) and are believed to have attacked large boats. Large sperm whale feed on them and sometimes get giant scars from their encounters.
Marlin, Sailfish, Swordfish and Sawfish
A few accidents have been reported by schools of fish stalking boats and impaling people (this is very rare). Most accidents happen while game fishing with the fish fighting for his freedom. Avoid using flashlights at nights in areas of schooling.
Most venomous fish known. Up to 12 inches long, perfectly camouflaged, it looks very much like a stone. Only dangerous if stepped on or caught. The dorsal spines can piece through a shoe. The pain is excruciating and can last for months with tremendous swelling and death of tissues. Amputation might be required. If not treated, stonefish stings can often be deadly.
Remove pieces of spines, encouraging bleeding might remove some venom, wash with water. Rest and elevate. If possible immerse wound in hot water (45 C or 113 F) for 30-90 minutes or until pain decreases. Then rest, elevate and dress with something clean.
On Site Treatment:
Local cleaning of wound and removal of broken spines should be treated with antibiotics (neomycin or bacitracin).
Local anesthetics (e.g 5-10 mg Lignocaine 2% without epinephrine injected through the punctured wound. Bupivacaine is longer lasting. Emetine HCl 0.5-1.0 ml at a concentration of 50mg/n\ml injected in wound site.
If given early: local injection into the site with hyoshine butylbromide (Buscopan), or emetine hydrochloride.
There are many species of stingrays among which some can also be fatal. The pain delivered is excruciating and can last for months accompanied with significant swelling. Stingrays arent aggressive. They lay on or near the bottom, submerged in the sand and only sting people stepping on them (or fisherman removing them from nets). Their sting can cause very deep lacerations and profuse bleeding.
To avoid stepping on stingrays, shuffle feet in shallow water while going swimming. If given the choice the ray will flee.
There are 330 species of scorpionfish. Like stonefish, many looks like rocks. They have venomous spines from which they inject venom. Although not as dangerous as stonefish, or stingrays, they should be treated the same way. The most famous are the lionfish or turkeyfish (also called butterfly cod), 30cm long, brightly colored red or brown fish. Beautiful (praised in aquariums). They are usually found in shallow water. The devil fish looks much more like a large stone. The red rock cod looks like a stone often with a red belly.
Catfish also have spines (3) attached to their dorsal and two lateral fins. They can be dangerous to handle, but catfish do not attack.
Beautiful tropical fish. There are many species all characterized by a scalpel like spine protruding from the junction of their body and tail. (They could be venomous). Injuries only happen when handling fish. Surgeon fish can also cause ciguaterra poisoning if eaten.
Very small in size (2 to 20 cm, 10 to 100g) the beautiful blue ringed octopus is found in shallow topical water and in tide pools. The rings can turn to a bright blue to show the change of mood of the octopus.
The bite might be painless, but this octopus injects a neuromuscular paralyzing venom. The venom contains some maculotoxin, a poison more violent than any found on land animals. The nerve conduction is blocked and neuromuscular paralysis is followed by death. The victim might be saved if artificial respiration starts before marked cyanosis and hypotention develops.
400 species of cone shells can inject venom, a few species only are believe to be dangerous. Effects may vary from being painless to excruciating pain. Salt water seems to make it worse. Paralysis including respiratory failure may occur.
Crown of Thorns
Starfish up to 60cm in diameter and with 13 to 16 arms covered with sharp spines. It is usually found in deeper water than other starfish. Effects: severe pain for a few hours. Possible bleeding. Possible inflammation, extending to swollen lymph glands areas. Symptoms may continue for weeks or months especially if spines are left in the wound.
There are 87 species of sea snakes classified in two categories. The bottom feeders (like the striped banded sea snakes) and the pelagic (like the yellow-bellied sea snake). Sea snake live in all tropical waters except the Atlantic. They can be recognized by their flat tail used for swimming. Their poison is 20 times more powerful than the one of the cobra, but they inject much less if they inject any at all. Some have a very small mouth and are unable to bite large prey. First Aid: Immobilization and pressure bandaging of affected limbs; CPR (cardiovascular failure is the first cause of death, renal problems is the second one); and antivenom to be administered in a medical facility.
Spines might contain some venom and bring infections. Very few fatal cases were reported (usually from respiratory problems), but most cases bring mild to severe pain for few hours to infections that could last for months, especially is pieces of spines are left in the wound. Removal of spines should be done surgically or with extreme caution not to break them more into the wound. Sea Urchin roe is a delicacy in many countries but poisoning may occur.
Note: During our expedition, we feed on sea urchins. We have researched the species which could be potentially poisonous and places with high poising cases, but havent found much information on the subject. If there are any specialists reading this, we would love to receive more information.
Various type of sponges can produce irritations and pain for long periods. In doubt it is best not to touch any sponge (even dead ones washed out on shores).
There are many species of tropical sea worms found under rocks and in coral. These can produce painful and itchy rashes lasting for hours. Antihistamine or steroid application might help.
There are 9000 species of invertebrates using nematocysts (stinging capsules) to immobilize preys or as a defense.
Chironex, also known as Boxfish or Deadly sea wasp
Considered to be the most venomous marine creature. Death can occur with minimal contacts. Chironex are found in the warm waters of Pacific and Indian oceans. All reported deaths (70) have occurred in northern Australia between November and April. When death does not occur, the pain is excruciating and often stings leave significant scars.
Portuguese Man Of War (Physalia)
Fatalities have been reported, but usually victims survive after suffering from excruciating pain.
Many other jellyfish species are found. Contact with those may vary from a mild local itch to severe burning with throbbing pain. Some can lead to cardio-respiratory deficiency.
This animal looks like coral and is often found on coral reefs. It has small invisible tentacles with nematocysts. Locally, effects may vary from minor irritation of the skin to excruciating pain. Nausea and vomiting for a few hours is possible if a large surface of the skin comes in contact with fire coral.
Some can produce the same effect as the physalia
The stinging seaweed is an animal that looks like a fern. The color varies between brown and green, but can also be white or purple. Sensation varies from mild stinging to extreme pain. The skin turns red after 30 minutes with itchy pustules that can stay for a week.
It is an invertebrate also called Lizard Nudibranch. Long of 1-3 cm, usually blue on his dorsal surface and white on his ventral surface. It has a characteristic inflated air pocket. This animal feeds on various nematocysts, and the effects of its touch varies depending on the nematocyst it consumed.
If tentacles of nematocysts are still stuck to the skin, they need to be removed gently. Be careful not to squeeze them as to not discharge more nematocysts.
Local anesthetic spray or ointment may remove some of the pain on minor stings. Tannic acid is believed to work well.
Give cardiovascular and respiratory assistance if needed.
The best anesthetic ointments in order of efficiency seem to be: Lignocaine 5%; Ultralan 0.5% and Lignocaine gel. Benadryl cream isnt as effective. Commercial creams dont work as long.
Severe itching may occur after a few days. Steroid ointments (i.e. hydrocortisone) could help.
Read the page: Survival at Sea
Read Scary Shark Encounter by Jean-Philippe Soule