The remoras /ˈrɛmərəz/, sometimes called suckerfish, are a family (Echeneidae) of ray-finned fish in the order Perciformes. They grow to 7–75 cm (2.8 in–2 ft 5.5 in) long. Their distinctive first dorsal fins take the form of a modified oval, sucker-like organ with slat-like structures that open and close to create suction and take a firm hold against the skin of larger marine animals. The disk is made up of stout, flexible membranes that can be raised and lowered to generate suction. By sliding backward, the remora can increase the suction, or it can release itself by swimming forward. Remoras sometimes attach to small boats, and have been observed attaching to divers as well. They swim well on their own, with a sinuous, or curved, motion.