Sea hare's also known as sea slugs include quite a number of different species that occur all across the marine waters of our planet. They are actually a type of mollusk (shelled animal) called a gastropod (or univalve). Gastropods have just one shell. The word gastropod itself comes from Greek words meaning "stomach foot", referring to the location of a gastropod's "foot". Sea hares get their name from the large tentacles which resemble the large ears of a hare or rabbit. Sea hares are herbivorous, and are typically found on seaweed in shallow water. It seems to be the case that some young sea hares are capable of burrowing in soft sediment leaving only their rhinophores and mantle opening showing. Sea hares have an extremely good sense of smell. They can follow even the faintest scent using their rhinophores, which are extremely sensitive chemoreceptors.
Most Sea hares have an internal shell but some species have no shell at all. Sea hares rely on camoflage for protection. Fishes tend to avoid Sea hares because they have a highly toxic compound called aplysiatoxin, which these slugs absorb from algae they feed on. The mantle of the slugs has many glands, one of which excretes a fluid-cloud when the animal is disturbed. The color of the fluid is white, purple or reddish, depending on the color of the pigments in their seaweed food source. Their skin contains a similar toxin that renders sea hares largely inedible to many predators.