Some of them are pretty scary, while others are totally harmless; either way, here are some of the biggest sea animals, ranked by size.

From deadly 'living fossils' to glowing sea angels, the ocean floor is home to creatures almost alien to us. Here are five incredible creatures straight from the deep.

Scientists are racing to save sea stars from extinction through breeding. Here's what they're learning about the different species—from arm-wrestling bat stars to bloodless blood stars.

Elephant seals are the largest animals in North America. They spend most of their lives in the open sea and are a top predator in the Pacific Ocean, where they live and can survive depths of up to ...

Whales are the biggest animals of all time. Heavier than elephants, wooly mammoths, and even dinosaurs! But they weren’t always the titans of the sea. Let’s rewind the clock around 50 million ...

Sea reptiles the size of whales swam off the ... The creature would have been one of the largest ever known, behind only blue whales and dinosaurs, say scientists. The ancient jawbone was found ...

This thrilling deep-sea fish was voted the world's ugliest animal by the Ugly Animal Preservation ... or 'Big Red', one of the largest jellyfish in the world. The fangtooth has teeth to spare ...