What is the smallest sea animal?

The smallest sea animal is a type of zooplankton called a copepod. Copepods are small crustaceans that are found in all oceans. They are typically less than 1 millimeter in size, and some species can be as small as 0.5 millimeters. Copepods are important members of the marine food chain, and they are eaten by a variety of animals, including fish, whales, and seabirds.