The vast brackish oceans support a variety of life, from massive schools to solitary giants. However one must keep their numbers in check, a massive predator with an apatite of fire. The Curosal Brawler Shark fills that niche in spades, strong and fast with unchallenged reign.
These are the descendants of speartooth sharks, a species of river shark from Australia. Once seeded onto a world without other predators, they diversity into various niches from speed hunters to ambushers. This specific shark is from a family of sharks title "Brawler Sharks", mostly taking out prey but trashing and brawling. This strategy is rather effective, as it overpowers and stun prey.
These sharks are found everywhere in the world, from the most northern of poles to warm tropical equators. Preying upon everything but the smartest of dolphins and toughest of plecos, everything else is on the menu for these beasts to feast.