Amphipods, or side swimmers as they are sometimes termed, are ubiquitous in the Great Lakes. They are small, laterally compressed crustaceans with a shrimp-like appearance, but without a carapace. Amphipods occur in vegetation, under rocks, on sand and burrowing deep in profundal sediments. Most of the 6000 known species of amphipods live in the oceans, but many are also found in freshwater and terrestrial environments.