Approximately 4,600 species of amphipods exist, but they are often known by other names. Amphipods that live in sandy beaches are frequently called sand hoppers or sand fleas, while those that thrive in freshwater habitats and marine beaches are commonly referred to as scuds. Yet, no matter what name they are known by, most amphipods are brightly colored and are similar in appearance to petite shrimp, generally ranging in size from four to ten millimeters. In the deep sea, however, some scavenger species of amphipods may obtain lengths of up to 140 millimeters.