Wandering Sea Anemone

Found during the days in a bundle like a heap of baked beans attached to rocks and sea-grasses or stranded in rock pools, then drifting, rolling and tumbling during the night feeding with its tentacles extended.
This is a stinging anemone and comes in various colours.
Indo-Pacific - Australia, New Zealand

Sea Anemones are large solitary polyps which have no skeleton. They have a basal or pedal disc which helps them crawl and dig into place, for some, once in place it is virtually impossible to move. Other smaller anemones move around the reef to feed at night.
Most eat plankton, but they are capable of eating anything caught in their stinging tentacles including quite big fish.
The fringing tentacles are configured in six or multiples of six.
Some sea anemones have a symbiotic relationship with sea anemones and some live commensally with various crabs, shrimp and brittle stars.