Great barracudas are large fish. Mature specimens are usually around 60–100 cm (24–39 in) in length and weigh 2.5–9.0 kg (5.5–20 lb). Exceptionally large specimens can exceed 1.5 m (4.9 ft) and weigh over 23 kg (51 lb). The record-sized specimen caught on rod-and-reel weighed 46.72 kg (103.0 lb) and measured 1.7 m (5.6 ft), while an even bigger specimen measured 2 m (6.6 ft) and weighed 50 kg (110 lb). Barracudas are elongated fish with powerful jaws. The lower jaw of the large mouth juts out beyond the upper. Barracudas possess strong, fang-like teeth that are unequal in size and set in sockets in the jaws and on the roof of the mouth. The head is quite large and is pointed and pike-like in appearance. The gill covers do not have spines and are covered with small scales. The two dorsal fins are widely separated, with the first having five spines and the second having one spine and 9 soft rays. The second dorsal fin equals the anal fin in size and is situated more or less above it. The lateral line is prominent and extends straight from head to tail. The spinous dorsal fin is situated above the pelvis. The hind end of the caudal fin is forked or concave, and it is set at the end of a stout peduncle. The pectoral fins are placed low down on the sides. The barracuda has a large swim bladder.
In general, the barracuda's coloration is dark green or a blue type coloration or grey above chalky-white below. Sometimes, a row of darker cross-bars or black spots occurs on each side. The fins may be yellowish or dark.
Barracudas appear in open seas. They are voracious predators and hunt using a classic example of lie-in-wait or ambush. They rely on surprise and short bursts of speed (up to 27 mph (43 km/h) to overrun their prey, sacrificing maneuverability. Barracudas are more or less solitary in their habits. Young and half-grown fish frequently congregate in shoals. Their diets are composed almost totally of fish of all kinds. Large barracudas, when gorged, may attempt to herd a school of prey fish in shallow water, where they guard over them until they are ready for another hunt.
Barracudas and humans
Like sharks, some species of barracuda are reputed to be dangerous to swimmers. They are scavengers, and may mistake snorkellers for large predators, following them in hopes of eating the remains of their prey. Swimmers have been reported being bitten by barracuda, but such incidents are rare and possibly caused by poor visibility. Barracuda generally avoid muddy shallows, so attacks in surf are more likely to be by small sharks. Barracudas may mistake things that glint and shine for prey. An incident of a barracuda jumping out of water and injuring a kayaker has been reported, but a marine biologist at the University of Florida said the type of wound appeared to have rather been caused by a houndfish.
Handfeeding or touching large barracuda in general is to be avoided. Spearfishing around barracudas can also be dangerous, as they are quite capable of ripping a chunk from a wounded fish thrashing on a spear.
Diamond rings and other shiny objects have been known to catch their attention and resemble prey to them. Caution should be taken when swimming near mangrove coastlines by covering or removing such items.