The sea tomato is an anemone that lives in the Mediterranean sea and belongs to the group known as polyp cnidarians and is similar to the more common Beadlet anemone. Sea anemones are closely related to corals, jellyfish and hydra.
This anemone lives in rock pools along the coast and in the shallower parts of the sea below low tide level, where I found these. They feed on small crustaceans, zooplankton and worms. It captures food by using its tentacles to poison and entangle prey. They can apparently inflict a painful sting on a person.
It is a beautiful sight when feeding.