Note: up to 50 cm, brown, black or grey in color. R. remora is different from other remoras in the family Echeneidae by the modification of their dorsal fin. The dorsal fin, which has 22-26 soft rays, acts like a vacuum and attaches to large marine animals such as whales, dolphins, sharks and sea turtles. R. remora cannot survive in still water as they need fast moving water over their gills for respiration.