Water

Water is an abundant blue liquid found in nearly any biome. Water forms the oceans on either side of a map. It is less abundant in a Desert and totally absent in The Underworld. It flows more freely than lava. Candles, Torches, and Flaming Arrows do not emit light underwater, but Glowsticks and some other light sources do. Torches are knocked free when water touches them.

Underground pools of water can be spotted by the glowing Jellyfish which spawn there. Water is only found down to a certain depth before being replaced by pools of lava and evaporates if it enters the Underworld. As of update 1.2, each biome has their own unique water color, and to change the water color in any biome you can use Water Fountains from the Witch Doctor in hardmode after defeating Plantera.

Upon submersion a player's breath meter will display how long they can remain underwater before they begin to take damage. The point where a player is considered submersed for purposes of the breath meter is a pixel above the eyes. This roughly translates to being able to breathe when standing in two full tiles of water, but will be at risk of drowning if the third tile starts to have any water in it.

If the player's feet are in at least a tile of water, movement is hindered noticeably and players cannot swim unless they equip certain accessories.

Items Interacting With Water

 * Flippers allow the player to swim upward by jumping repeatedly from any point within the water.
 * Gills Potion allows the player to breathe underwater.
 * Breathing Reed allows the player to breathe while in shallow water and also increases the breath meter.
 * Diving Helmet increases the breath meter.
 * Diving Gear increases breath meter and allows swimming.
 * Neptune's Shell allows the player to breathe underwater and allows swimming.
 * Water Walking Potion, Lava Waders, Obsidian Water Walking Boots and Water Walking Boots allow the player to walk on the surface of water.
 * Pumps and Buckets can move water.

Mining Underwater
When mining in the underground, players will often encounter water. Players can avoid the water by simply mining around it. Alternatively, the water can be removed by either pumping or draining the water into another cavity. Either dig an outlet at one edge or from the bottom of the pool.

To produce light underwater, remove a block a little way into the wall so that it forms an air pocket and place a torch there. Alternatively, Glowsticks may be used when digging underwater. They provide less light but will work underwater, and can be thrown. These are especially useful when digging downward, because Glowsticks fall when the block beneath them is removed. This way, players can dig and light their way at the same time. Flares from a Flare Gun can also be used in this manner. If they are available, a Mining Helmet or an Shadow Orb (item) (Orb of Light on console) provide easy hands-free lighting. Players can also create a permanent underwater light source using a Cursed Torch (which functions like a normal torch, but with the added benefit of working underwater), although those can only be acquired after hardmode is activated.