Pipefish (family Syngnathidae) are slim, elongate fish with large heads and extended, tubular mouths. The extended snout frequently measures more than half of the total head length. The body is enclosed in a tough, segmented skin and the fins, with the exception of the dorsal fin, are greatly reduced in comparison to other fish. Pipefish are widely distributed in tropical and warm-temperate waters; most species are marine but some freshwater species are also known from the tropics. Most species live in shallow waters, usually less than 65 ft (20 m) in depth. Many are estuarine-dwellers. Pipefish are masters at concealing themselves from predators: those species that live in and around seaweed fronds or sea grass beds align themselves with the vegetation and drift with the current, appearing as additional floating fragments of vegetation.
Most pipefish are a dull green or olive color, but many are ringed with more striking colors. Some species can alter their background color to help blend in with their surroundings. Successful camouflage is also an advantage when stalking prey. Small fish, for example, are hunted visually: when the pipefish is within striking distance, they are snapped up with a rapid lunge, the open mouth and tubular snout being extended at the same time. A wide range of small crustaceans are also eaten.
Pipefish swim in a leisurely fashion, characteristically in an upright position, gliding slowly through the water by means of rapid wavelike movements of the dorsal fin. Should they need to move faster, they can propel themselves forward by bending the body over and moving forward in a series of jumplike movements.
Breeding may take place throughout the year in the tropics, but is limited to June through August in more temperate waters. As with the closely related sea horses, parental responsibilities in pipefish belong to the male. Male fish incubate the developing eggs either in a shallow groove on the underside of the tail or in special folds of soft skin on the abdomen. Some species carry the eggs directly attached to the abdomen, the female having laid them there directly. The young fry, which may measure just 0.35 in (9 mm) in length, are free-living and free-swimming but remain close to the adult male for several days after hatching.