Shark

The Shark is an enemy that is found in the Oceans on either side of the world. They have 300 health (making it the the in pre-hardmode monster with the most health, other than the Dungeon Guardian) and can do decent damage, making an Ocean a dangerous place. Sharks only spawn within 250 blocks from the edges of the map and will not spawn anywhere else.

Strategy
Sharks charge directly at the player and can move more quickly than the player. They are highly resistant to knockback, but strong weapons unable to knock them back will usually at least halt their advance. Rapid-fire weapons and flails tend to be more effective against Sharks—the Aqua Scepter, in particular. Spiky Balls, when thrown while on the Ocean floor, are also very effective, as an approaching Shark will ram through them, quickly taking all three hits.

Alternatively, just using a boomerang or flail from outside the water can quickly bring down a Shark. The locally available Trident is highly effective in this regard, as it will always hit three times as it passes through the Shark.

You can drink a Water Walking Potion and the shark will ignore you and swim away when you are standing on the surface. Diving below the surface will get his attention again. Having the Flipper accessory will keep you from sinking to the bottom. Use a boomerang to finish him off.

Yet another method of farming/defending is to dig a spot to stand on—but still be inside water (but not drowning)—and then to add a shield of blocks in front of this standing section to one tile above the water's surface. The player can then use a ranged weapon or weapons such as the Flamelash or Magic Missile—or even bows or Grenades—over the barrier.

A similar method is to stay on the Ocean floor, create an arc shaped section of blocks, destroy the part connected to the ground, and stand within the arc. Sharks will then try to attack by going under it, but they won't fit. From there, the player can attack with impunity. Lacking proper swim gear, a stack of Gills Potions may come in handy for this approach.

Another approach is to make an area that only you can fit (2x3) and dig two spaces down or to the side (to get rid of water) and fill it up again. Then you can breathe while (technically) being underwater. Then use a sword such as Vilethorn or Starfury etc. so you can attack through blocks.

History
Requin Shark Shark Акула