On the lower shore sponges can be found beneath rocks. Many are thousands of individual tiny individuals living together. They are simple animals. They absorb water and filter particles of food.
Photo: Paul Naylor www_marinephoto_co_uk
Form normally in thin areas of seaweeds. rocks, and seashells. Often feel chalky or slimy to touch and are made up of tiny animals called Zooids. Each animal is a kind of box and has a crown of tentacles.
Similar to sponges, these are complex animals. Some live in colonies and others are single. Can grow large, If gently squeezed, can squirt out a jet of water from it’s openings.
Sea Squirts – https://en.wikipedia.org/wiki/Ascidiacea