Barracuda actually encompasses a decently sized family of fish (sawtooth, Pacific, great, red, blackfin, and more). However, the differences are marginal, so we'll cover them all together. Over time you should start to look up the species and study the differences. At the least, you should learn the species that live in the region where you dive.
Barracuda have long, streamlined bodies that are rounded in the middle. Some species (like the great barracuda) can reach up to 1.8 meters (almost 6 feet!) in length, while most are a couple of feet long.
Most species have a distinctive underbite, which means their lower jaw appears to jut out, revealing a nasty set of teeth. Their teeth are fang-like, sharp, pointed, and all different sizes.
Barracuda can be anywhere from brownish to bluish gray on their upper body, with silvery sides leading to a white belly. Many species may have around 20 dark bars on their upper sides. If you see dark spots on the lower sides, you are probably looking at a great barracuda.
They have a rear dorsal fin paired with an anal fin right below it. They do have a forward dorsal fin, but it is usually flat and not visible. The caudal fin is moderately forked and suggestive of their swimming power.
Geography and habitat
Barracuda live in the tropical and subtropical regions across the globe. Most species spend their time near shore in coral reefs or mangroves. Some larger species are found in the open water, usually near the surface.
Barracuda tend to be solitary fish, hovering above reefs waiting to dash at prey. Younger barracuda, however, are sometimes seen in a group, called a battery.
Danger to humans
If you've ever caught sight of a barracuda watching you, it can be quite unnerving. In reality, they are of little danger to humans. It is true that wearing shiny jewelry and speared fish can attract the attention of a barracuda. Despite this, an attack is unlikely to be serious, at worse requiring stitches.
Be careful while spearfishing and avoid shiny objects and the chances of an attack are reduced to negligible.
Photo by JennyHuang