A Shark is a hostile aquatic mob that is commonly found in Oceans and swimming around in most bodies of water.
When the player enters the water, any Shark nearby will turn on them and swim very fast towards them to chase down and attack the player. They don't attack Squids or other Sharks.
Sharks have a 10% chance of dropping a Shark Egg when killed. The egg can only be obtained if the difficulty is on Easy difficulty or higher.
In order to get a tamed Shark, the egg must be hatched by throwing it into the water, which will hatch into a friendly baby Shark. Once it grows big enough, it will attack other Mobs. Tamed Sharks will not attack other Sharks or the player.
There is no current way to heal a tamed Shark by "feeding it" (as is possible with other tameable mobs). The only way to heal a tamed Shark is to throw a Splash Potion of Healing at it.
Sharks can not be ridden or bred, unlike Dolphins.
Note: If you are playing on Creative Mode and want a Shark egg, then use this command: /give [username] MoCreatures:mocegg 1 11 as of 1.7.10.
Other than for crafting Chain Armor, Shark Teeth can also be used to craft the Shark Sword, which is a weapon unique to the Mo' Creatures Mod and a Fish Net. As of DEV v8.0.0 for Minecraft 1.8, Shark Teeth can be used to craft Bone Meal.