13 Dangerous Fish and Sea Animals

A scuba diver watches a stingray.

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Sea animals and fish are frequently the victims of negative publicity. More often than not, browsing through wildlife documentary channels on television will reveal a disappointing trend. Many of the documentaries have names such as "Killer Squid" and "The Deadliest Octopus." No wonder some new divers are frightened by aquatic life!

Marine animal behavior can appear threatening to divers who do not understand the purpose behind the behavior. Many sea animals look threatening but are completely docile, and some animals that appear friendly can actually be quite aggressive.

Almost all aquatic life injuries to humans are caused by defensive behavior on the part of the animal. As long as you don't try to pull eels out of their holes, poke the lobsters, or attempt to ride the stingrays, you should be just fine. Don't bother the fish and they won't bother you.

Learn about some of the animals that divers commonly fear and to discover which are dangerous and which are not.

01 of 13

Moray Eels - Not Dangerous

A moray eel in a rocky reef.

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Moray eels are large, marine eels commonly found sheltering under ledges or inside holes in the reef. New divers may find eels frightening because they have visible sharp teeth and because they hang around with their mouths open as if they are about to bite. This behavior, which may look like an eel is threatening divers, is really just a way for the eel to pump water across its gills to breathe. The only danger from eels is that they have terrible eyesight and may mistake a prodding finger or dangling piece of gear for a fish. Give moray eels space and they pose no threat.

02 of 13

Coral - Dangerous If Touched

A scuba diver swimming near a coral reef.

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One of the most common marine life injuries from scuba diving is scraping against coral. A coral head is composed of a hard (sometimes sharp) limestone support covered by thousands of tiny coral animals. A diver who contacts the reef may be cut by the sharp limestone or stung by coral polyps. Depending upon the species of coral, these injuries range from minor scratches to stinging welts. Of course, a diver can avoid coral injuries completely by maintaining good buoyancy and awareness to stay clear of the reef.

Not only is making contact with coral dangerous to divers, but it's also dangerous to coral. Even the gentlest touch of a diver's fin or hand may kill delicate coral polyps. A diver who touches the reef does more damage to the coral than the coral does to him or her.

03 of 13

Stingrays - Not Dangerous

The underwater world of the Cocos Islands
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A stingray's pointed and sharp stinger may frighten new divers. However, stingrays are anything but aggressive. Common stingray behavior includes the stingray burying itself in the sand for camouflaging and beating the sand with its wings and nose to look for food. Stingrays will occasionally swim calmly beneath divers. This is not threatening behavior but is a sign that the stingray is relaxed and unafraid.

When approached closely by divers, most stingrays either freeze in an attempt to remain ​invisible or flee the area. A stingray will only sting a diver as a last, desperate defense. Never trap, grab, or press on a stingray's back. Allow stingrays space and the opportunity to escape and they pose no threat.

04 of 13

Jellyfish - Dangerous but Rare

Snorkeling Jellyfish Lake
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A jellyfish sting can injure a scuba diver. However, jellyfish stings are rare because these animals do not attack divers. The danger with jellyfish is that they frequently have long transparent tentacles that are difficult to spot, so a diver may accidentally swim into them.

Before diving in a new location, a diver should talk to local divers (and ideally sign up for an orientation dive with a local guide or instructor) to learn about hazards such as jellyfish. Most jellyfish stings can be avoided by wearing a full wetsuit or dive skin to prevent inadvertent contact with the tentacles.

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05 of 13

Lobsters and Crabs - Not Dangerous

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Lobsters and crabs have powerful claws for crushing prey (such as clams) and for defense. Their claws are not for pinching divers. As divers are not the typical lobster/crab prey, a diver need not fear these crustaceans' claws unless he or she is threatening the animal. A diver who does not attempt to extract lobsters or crabs from the reef and instead enjoys observing these colorful creatures from a respectful distance will not be pinched.

06 of 13

Sharks - Not Dangerous Unless You Feed Them

Underwater Scenes
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Sharks are probably the most misunderstood creatures in the ocean. They are aggressive predators, but scuba divers are not their natural prey. Most sharks appear shyly curious if they encounter divers underwater. Something about a diver's noisy bubbles and bug-eyed mask must scare them off. The few shark-related diving injuries that do occur generally happen when scuba divers feed these animals. When fed (especially by hand) sharks sometimes become frenzied and may mistakenly nibble a diver. For this reason, divers should never feed sharks or other marine life without the supervision of a professional.

07 of 13

Damselfish - Aggressive, but Not Dangerous

A damselfish approaches a diver.

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With all the ugly, toothy, and spiny fish in the sea, the last fish a diver may be expecting to attack is the damselfish. Damselfish are relatively small (about 3-5 inches in general) and sometimes very pretty. Damselfish are dedicated gardeners, tending a small algal patch which provides their food. If a diver violates the damselfish's territory, the angry little fish will aggressively nip at the diver. Most of the time this is fairly comical, and it is rare that these tiny fish manage to do damage.

Perhaps the most aggressive of the damselfish is the Sergeant Major. Normally docile, the males of the species becomes very defensive when tending eggs. To warn other fish (and divers) that he means business, an egg-tending male will darken his white body to blue or indigo. Give blue Sergeant Majors space unless you want to be nibbled.

08 of 13

Sea Urchins - Dangerous to Touch

Sea Urchins
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Like coral, sea urchins do not pose a danger to conscientious, controlled divers. However, a diver who is out of control or unaware of his or her surroundings may accidentally touch an urchin, which will result in quite a shock. Sea urchin spines are sharp and brittle and can easily penetrate a wetsuit and break off under a diver's skin. In addition, certain species of sea urchins defend themselves by injecting a painful venom into creatures that touch or attack them. As long as a diver is careful to touch nothing while underwater, he or she can be certain to avoid a sea urchin sting.

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09 of 13

Triggerfish - Dangerous

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Some species of triggerfish are friendly, and others defend their territory against intruders. An example of a highly aggressive triggerfish is the Titan Triggerfish. Titan Triggerfish are found in the Indo-Pacific Ocean. They are quite large — over a foot long — and have specialized teeth and powerful jaws. Titan Triggerfish will defend their nests and territory violently, biting and butting at intruders.

These fish have been known to seriously injure divers and should not to be taken lightly. Many experienced divers are more nervous around Titan Triggerfish than any other species. Dive briefings in locations with dangerous triggerfish usually include a clear explanation of how to identify the triggerfish, and what actions to take if an aggressive triggerfish is spotted. Stay with the dive guide and follow his or her advice. In many cases, guides can help divers to avoid dangerous triggerfish territories.

10 of 13

Remoras - Annoying but Not Dangerous

Sea Turtle with Remoras
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Remoras are large, gray, parasitic fish usually found stuck to the sides of sharks, manta rays, and other large species. Remoras are not dangerous to their hosts. They simply attach to the larger animal and hitch a ride. While attached to a host, remoras snack on scraps of meals and waste matter from the larger creature. In some cases, remoras will clean bacteria and small parasites from the host.

Unattached remoras can make themselves obnoxious to divers. Perhaps not the brightest of creatures, remoras seem to attach to anything large and moving. Divers fit into this category. Remoras have been known to attach to a diver's tank or body. As long as the diver is covered by a wetsuit, the remora does no harm. Most encounters with free-swimming remoras are comical, as they mistakenly attempt to suck onto a diver's tank and limbs. However, a remora that attaches directly to a diver's skin may cause a scrape. This is yet another reason to wear a full wetsuit or dive skin.

A remora can usually be frightened away by purging a regulator alternate air source in its face.

11 of 13

Barracuda - Generally Not Dangerous

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Scuba diving myths are filled with stories of barracuda attacking divers. This fish looks scary to many divers — it has a mouth full of sharp, protruding teeth and moves at lightning speed. However, barracuda attacks on scuba divers are extremely rare.

As with most aquatic life injuries, barracuda attacks are almost always either defensive or mistaken. A human who attempts to spearfish a barracuda and misses or only injures the animal may find him or herself on the receiving end of defensive action. A person who feeds a barracuda or other fish near a barracuda may get nipped accidentally. There are also unconfirmed stories of barracudas mistaking reflective or sparkling objects for prey — such as diamond rings and shiny jewelry. If you leave jewelry on the surface and don't hunt or feed these fish, they should pose no danger.

12 of 13

Lionfish - Dangerous to Touch

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Lionfish boast an array of colorful, featherlike quills. Their color and patterns help lionfish to camouflage with the reef, and they may be difficult to spot. Most lionfish injuries in the Indo-Pacific are caused by inadvertent contact with a well-camouflaged fish. In the Atlantic, increasing numbers of divers attempt to remove invasive lionfish from the reef because they are disrupting the food chain. A lionfish hunter may accidentally come into contact with the painful sting of the lionfish as he tries to remove it.

As with many other spiny fish species, lionfish spines release a powerful neurotoxin when touched. The sting of a lionfish is excruciatingly painful and may lead to severe allergic reactions. Avoid contact with lionfish, and all other aquatic life. Train to hunt lionfish with an experienced lionfish hunter in order to learn safe hunting and removal techniques.

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13 of 13

Humans - Dangerous

A scuba diver watches fish swimming near a reef.

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The most hazardous creatures to divers are probably the divers themselves. A diver is exponentially more likely to injure him or herself through neglect of proper diving protocols, inadequate dive skills, or human error than being attacked or injured by marine life. In fact, most aquatic life injuries are caused by the action of the diver.

Divers may purposefully or accidentally touch a dangerous creature or provoke an attack by making an animal feel threatened. Unprovoked marine life attacks on scuba divers are exceptionally rare. As a general rule of thumb, give animals space and observe them respectfully and calmly from a distance. Never chase, touch, or corner a marine species. Don't harass the animals and they will not harass you.