Image of Jack sail-by-the-wind

Description:

Quite a few of these floating around in the tidal gut. It was an outgoing tide but they were coming in. I did observe one in a rock pool moving along and turning around while all of the others in the pool were stationary - and that rock pool had no water movement whatsoever. I do not have a clue what they are or where to start so I thought I would be creative and start with a bluebottle sea anemone :D The first photo is taken looking straight down and the second photo is from the side.