Add sharks as a helpful mob (like dolphins)

Many people have already suggested neutral sharks, but I have a proposed spin on it that would make it far more unique than most others.

Polar bears are a clear demonstration that a naturally extremely dangerous and aggressive creature can be added as a neutral or even friendly mob in the game for environmental awareness purposes. So rather than making them purely neutral, or even randomly biting the player occasionally like they do irl (or as others have suggested), I propose a different method of interacting with sharks that is also rooted in reality. 

Sharks will naturally attempt to hunt certain fish, perhaps normal, perhaps the nautilus, perhaps something new entirely. However, these fish will hide in coral reefs or small pockets in the ground, which keep sharks from reaching them under certain circumstances.

Should the player choose to kill these fish for the shark and feed them to it, the shark will defend the player from hostile mobs and lead them to buried treasure, ruined portals, shipwrecks or underwater archaeological structures. This is rooted in behavior in which sharks will bump the points of harpoons or tridents to indicate they want a scuba diver to kill lion-fish with them so they can eat them. 

This idea should hopefully walk the line of not conflicting at all with existing endangered animal representation while also keeping them unique and interesting, arguably moreso than even the polar bear.