Cnidaria

The innocuously named sea walnut, a jellyfish, is actually an effective and stealthy predator, according to scientists.

It takes a lot of stinger-equipped tentacles.

The box jellyfish is pretty...pretty poisonous.

Clues to the a jellyfish's deadly sting may lead to an antidote.

Sea creatures stir the world's oceans.

A "jellyologist" explains the mysteries of large swarms of jellyfish that can cover hundreds of square miles of ocean.

Here's lookin' like you, babe. Jellyfish have many eyes that serve different purposes. One set works like ours.

In a region off the west coast of Africa, jellyfish are taking over. Similar scenarios play out around the globe.

Ships to blame, scientists say while also announcing 16 new species.