How do marine invertebrates find their prey?

Many marine invertebrates, such as corals and sponges, are filter feeders and siphon water through their bodies in order to filter out small fish, plankton, and other floating debris.  Others, such as sea urchins, act as scavengers and feed upon whatever they find on the ocean floor, including the remains of dead animals.  Many marine invertebrates rely on camouflage in order to surprise their prey and others sting their prey with their tentacles or spines.  In other instances, marine invertebrates may act as parasites or they may have a symbiotic relationship with another creature.