Sharkolotl

Humorously named due to the fact it looks like a cross between a shark and an axolotl, a Sharkolotl.

Contrary to its naming scheme, the Sharkolotl is entirely related to the Axolotl family and has zero relations to sharks. It's believed it is the result of Axolotls exposed to salt water and either luck of an unknown mutation or clever use of magic allowed a few to survive the experience. Overtime, due to the ocean's crueler nature, the humble Axolotl had to evolve to a larger, stronger design suited for the environment in order to improve survival chances.

It's impossible to fully domesticate them for now, but isn't impossible to "tame" one. Otherwise known as having it adjust to one being around it, which greatly lessens the risk of danger.

There are some similarities in biology with their normal cousins, however, they're more suited for a saltwater environment. They entirely lack their hindlegs, them being fused with their tail due to no longer needing them. They developed retractable teeth and dexterous hands for aid in hunting rather than relying on inhaling their prey. And the most notable add on to their features are the fins that are extremely similar to a shark's fins. It should be noted that no one has yet figured out their maximum natural lifespan. 

Intelligence wise, Sharkolotls are instinctually intelligent hunters, capable of knowing when something is worth the effort to consume or test biting objects before attempting anything else. Like their freshwater cousins, they are entirely silent due to lacking vocal cords, the noises made being from breathing whilst surfacing sounding akin to hiccups, barking or squeaking. Their communication is done through body language and touch. Normally, they are generally safe to be around unless they are in search of food and mistake one for prey, or in the event one is dumb enough to annoy it. Unlike their cousins, Sharkolotls can form a group to increase both safety and hunting efficiency. They are also occasionally seen joining other marine life during feeding frenzies.

Their population has managed to remain stable and are common amongst their habitats. Their evolution and behavior allow them to compete with other aquatic species, but their size and the fact the ocean is a hellhole makes them prey still to bigger fish. The Sharkolotl's diet consists mainly of whatever sea life they can kill and consume; they are not picky eaters, if it is worth the energy to hunt, they will hunt it.

Sharkolotls can, regretfully, be eaten by humanoids who are capable of either fishing or spear fishing them. While usually not intentional, there has been Sharkolotl attacks in the past due to test bites or individuals doing behaviors that remind Sharkolotls of prey. As such, while they are considered peaceful, it's not recommended to test how far that peacefulness can go.

However, like with the Giant Axolotls, there is supposedly a City-State revering them as more sacred creatures, going as far as to occasionally feed them whenever encountered.

Like their freshwater cousins, Sharkolotls possess regenerative capabilities. However, this process is a lot faster, working in moments rather than taking months. Unlike their freshwater cousins, however, they use their vacuum-like ability to instead further enhance their speed, by forcibly pulling water into the mouth and forcing it out the gills.