Desbreko are often found right alongside their Skullfish brethren. If Link does happen to defeat a Desbreko while Skullfish are around, all of the Skullfish will also be defeated. Unlike most enemies in the game, a Desbreko won't immediately disintegrate once it is defeated. Instead it will begin to float up towards the surface before eventually doing so.
Desbreko will move around within the water and once they spot Link, they will quickly swim over and try to cause harm. Desbreko often times attack in groups, along with smaller Skullfish.
There are a few ways to kill these pesky enemies and it is most safe to do from the surface if you can. From here, Link can use the Hookshot, shoot it with an Arrow, or Zora Link's Boomerangs. While in the water, Link can defeat a Desbreko using the Electrical Barrier attack.
It's a Desbreko.
In the Japanese version of the game, Desbreko are known as Death Pleco, which comes from Plecostomus, which are freshwater fish that are sometimes referred to as suckermouth fish.