Yellow Colonial Ascidian

Found in dense colonies, in shallow waters, over hard substrates, of channels, lagoons, and seaward reefs. Not very common.
They feed on detritus and suspended plankton.

Ascidian, also known as tunicates because their bodies are covered by a "tunic" a tough cellulose-like covering.
The other common name is sea squirt because when threatened they sometimes eject a jet of water.