8 of the World's Most Dangerous Fish and Sea Animals

What are the most dangerous sea animals

Hopping off the boat for a little dip is a wonderful idea from time to time, but what lurks under the water can spell instant disaster for the unwary diver.

We'll look at the top eight most dangerous sea animals today. Realize that this list could be endless so if you don't know what capabilities a certain fish has, it's probably a good idea to steer clear.

The most generous members of this list are extremely colorful and vibrant. It's quite kind of them to warn us to steer clear. Or maybe they're trying to lure us in... Hmm.

There are also others that are just as venomous, and much more sneaky about their tactics. Always watch where you're putting your hands and feet when diving.

8 of the World's Most Dangerous Fish and Sea Animals sharks


Are sharks truly dangerous? No. Not really. Unless you're a fish, that is. Divers are not the shark's natural prey, so they generally just want to investigate the strange surface-dwelling visitor and usually won't bite. 

That can change quite quickly if you decide to feed them. A feeding frenzy will ensue, and you might end up being accidentally nibbled. You better believe that even an incidental nosh can cause major damage through almost anything aside from shark-mail armor.

Stay calm, enjoy the majesty of the sharks if they decide to visit, but never ever EVER feed them.

8 of the World's Most Dangerous Fish and Sea Animals triggerfish


I hate triggerfish. They're beautiful and useful ocean animals, but some species are just so territorial that they can truly harass wayward divers. The titan triggerfish of the Indo-Pacific Ocean can grow around a foot long, and they have nasty little teeth attached to even nastier jaws.

They will bite and ram divers while easily shredding through a full wetsuit. Plenty of divers have been caught off guard and been seriously injured. Approach with extreme caution, or better yet? Don't approach them at all.

8 of the World's Most Dangerous Fish and Sea Animals jellyfish


There are a ton of jellyfish out there. I've been caught by exactly one, and it's a day I'll never forget. Plenty of these dangerous sea animals aren't lethal to humans, but the ones that are, do what they do very well.

Probably the most notable examples are the box jellyfish and the Portuguese man o' war. They're translucent in the water and have long tendrils that are almost impossible to see.

Keep your eyes peeled and do your darndest to stay clear of anything that looks similar to a jelly. I've swum away in terror from what was a plastic bag. My spouse thought that was a real hoot but I say better safe than sorry!

8 of the World's Most Dangerous Fish and Sea Animals sea snake

Sea Snakes

There aren't a lot of people on the planet who like snakes. Heck, even Indiana Jones is afraid of them. But they lurk among coral reefs, and many of them have an extremely deadly bite.

Fortunately, they aren't very aggressive and if you see one swimming toward you, he's probably just curious about this bug-eyed creature making all the noisy bubbles near his home. Stay calm and he will eventually move on.

8 of the World's Most Dangerous Fish and Sea Animals stone coral

Stone Fish

There are a lot of entries on this list from the suborder Scorpaenidae. Some are the vibrant sort we talked about, but the majority are well camouflaged.

The stonefish is so-called because it settles under the sand. You might not notice it at all until it's stepped on. Luckily it's only found in waters north of Australia.

The dorsal spines don't release venom unless pressure is applied, which makes them sort of innocent stingers. Their sting can be fatal, so step with care.

8 of the World's Most Dangerous Fish and Sea Animals lionfish


The lionfish is another cousin of the Stonefish and Scorpionfish. Without a doubt, it's the most flamboyant of the bunch. These little guys are extremely easy to spot and aren't aggressive.

While their sting doesn't kill, you'll still want to keep a distance. That should be easy enough... Unless you're in the Caribbean. Lionfish have been introduced to these waters and have been out-competing native species, so what's the obvious solution? Cull lionfish in the Caribbean! Unfortunately, this has led to free-floating spines or corpses that make diving in Caribbean waters a riskier prospect.

8 of the World's Most Dangerous Fish and Sea Animals coral reef

Fire Coral

There are plenty of coral species, and most of them will give you a nasty scrape if you drag exposed skin along them. These scrapes are certain to hurt as they'll be submerged in saltwater the moment they occur, but that pain is nothing compared to the agony caused by a brush with the fire coral.

It isn't deadly, but you might wish it was for a bit. The burn is intense, like that of a stinging nettle. There are plenty of other corals that aren't as easy to identify, so a good rule of thumb is to simply not fiddle with coral at all. It takes ages to grow and humans can cause irreparable damage. It's actually illegal in most areas to even touch coral. So, just don't do it.

8 of the World's Most Dangerous Fish and Sea Animals sea urchin

Sea Urchins

Touching bottom while diving is generally an activity to be avoided. Sea urchins are generally stationary and you can spot/avoid them if visibility is good. However, if you're lacking awareness or are just out of control during the dive, you might have the bad luck of experiencing a sea urchin's sting.

Sea urchins have spines that will break off under the skin. Even if that doesn't happen, you'll probably still never forget the day that it happened. Pain is a very good teacher.

While You're Down There...

Diving is a great opportunity to commune with some sea animals, dangerous or otherwise. But you might also take the chance to inspect the underside of your vessel.

A quick scrub with a firm 8" boat brush can grant a new lease on life without needing to dry dock your boat. If you uncover any suspected cracks while you're scrubbing, a quick dollop of our marine sealant & adhesive caulk could save the day, lest you have to swim with the fishes for longer than intended.