1. Three Main Groups of Plants and Animals in the Ocean Plankton Plankton are the plants and animals that drift on the top of the ocean. They include algae, protozoa, jellyfish, and the larvae of many sea animals. Plankton drift passively and are moved by ocean currents. They have no other means of movement. Plankton make up the base of the ocean food web. All other forms of life are dependent on their existence. In return, the plankton is dependent on the sun for survival. That is the reason these ocean creatures are only found at the top of the ocean zones. Benthos Benthos are the ocean creatures that live on the ocean floor. Benthos include seaweed, crabs, clams, lobsters, and sea urchins. Some of the benthos, such as seaweed, are anchored to the ocean floor. Many of the animals in the group are able to move on their own legs. All of the sea life in the benthos group may be moved by ocean currents, but they are not passively dependent on it as the plankton are. Coral reefs provide an amazing ecosystem of many types of benthos and nekton. Nekton The nekton are the animals that swim in the ocean. This group includes fish, shark, whales, sting rays, and many other swimming animals. Different nekton live at different zones of the ocean. Their diet may be made up of plankton, benthos, or other nekton.