The delicate Burrowing Anemone, Cerianthus lloydi, is common on soft ground all around Britain. It lives in a slimy tube buried in the ground and projects its sixty tentacles in a flower-like arrangement around it. These tentacles can be up to 4cms in length and there are a similar number of shorter, inner tentacles. The anemone will vanish into its tube in an instant if disturbed.
In the picture, which was taken from directly above, the ground around it is covered in red algae.