It’s a Sea Anemone;And WTF is pic #5? That's gotta be a movie prop or sumpin'...
Dofleinia armata is one of Australia's largest species of anemone. It can grow to 20 cm in diameter, with tentacles up to 50 cm long.
The base of this species is broad, the column smooth, with a broad, flat oral disc. It has long inner tentacles which are a minimum of double the size of the outer tentancles. The tentacles have visible papillae on the surface. These contain nematocysts that are very large. The oral disc has papillae as well, but weaker. These contain nematocysts also.
The surface of the tentaces end in a tip that is somewhat swollen. The tentacles are either cream, brown, or plain, and are striped. They have a surface that is scale-like and are often observed curling into ball shapes that hide the mouth.
It is able to expand its body and tentacles due to a well-developed hydrostatic system.