Sea creatures riddles

I have eight legs and three hearts. I don't have any bones.

Oceans, rivers, lakes, ponds, everywhere there is water I can live. Sometimes I live with you in a bowl.

I am the biggest animal in the world, and not a fish. I eat very small animals called plankton.

I am scary and I eat fish and sometimes people. I am big or small, and I have lots and lots of teeth.

I have a long tail and a head like a horse. I don't have stomach or teeth.

I am very clever and swim fast, I look like a fish but am a mammal. I breath air like you.

I float in the water with long tentacles. I sting fish or people.

I am a slow sea animal, I have a hard shell and four legs.

I move slowly on the ocean floor with my star shaped body. I can be so many colours.