These jellyfish have tentacles that contain powerful venom that can cause heart failure and death in humans.
Great white shark
Known for their size and powerful bite, great white sharks are one of the most well-known and feared sea creatures.
Saltwater crocodile
The largest living crocodile species, saltwater crocodiles have been known to attack and kill humans.
Portuguese man o' war
Though it is often mistaken for a jellyfish, the Portuguese man o' war is actually a siphonophore and has tentacles that can deliver a painful sting.
Blue-ringed octopus
These small but deadly octopuses are found in the Pacific and Indian Oceans and carry a toxin that can cause respiratory and muscular paralysis.
Stonefish
These bottom-dwelling fish blend in with their surroundings and have venomous spines that can cause extreme pain and even death.
Lionfish
Originally from the Indian Ocean, lionfish have become an invasive species in the Caribbean and Gulf of Mexico, and have venomous spines that can cause intense pain and swelling.
Saltwater crocodile
The largest living crocodile species, saltwater crocodiles have been known to attack and kill humans.
Tiger shark
Like the great white, tiger sharks are known for their size and power, and are responsible for many attacks on humans.
Cone snail
These snails have venomous harpoons called "radular teeth" that they use to paralyze prey, and the venom can be lethal to humans.
Barracuda
Known for their sharp teeth and aggressive behavior, barracudas can attack humans when they feel threatened.