Water

Water is a liquid found in pools of varying size on both the surface of the world and underground. If the player is underwater, the breath meter will start to decrease. If the breath meter is depleted, the player will rapidly lose health. If water touches lava, the lava will become Obsidian, and vice-versa.

The player can stay underwater for approximately 25 seconds before they start taking drowning damage. This time is indicated by a special "Breath" meter, that appears below the Health bar. Movement is also slowed down to about 50% of normal speed while in water. When the player is considered underwater, and the Breath meter will begin to drain, when the water level is at about the same area the mouth would be on the player's head.

In small to medium sized pools of water, mining away solid blocks will cause water to fill into those spots. This can lower the level of the pool, as the water sinks lower to fill in the newly emptied space. When underground, the pools will attempt to flow into any available empty space below as the land is dug out.

A bucket can be used to move water, by filling the bucket and dumping water out. This is a good way to move around small amounts of water, for either cosmetic purposes, or removing smaller pools. This is a fairly inefficient means of removing large amounts of water, if the player intends to completely empty an area of water. It is possible to create an unlimited source of water, with wires and pumps, but an easy way for new players is to make a wide 1-block deep pool ( 10-20 blocks wide should do), fill ONE bucket of water, place it in the pool, then make a 2 block by 2 block underhang beneath and area with water that is NOT ON THE EDGE, like a cube hanging to the bottom, but 2 blocks tall/deep and 2 blocks wide. remove the upper right block of your little cube, and then break the block above it. Voila! Endless water, perfect for the people who want to make a water village with waterfalls.

Before patch 1.1, one means of removing water was to fill an entire pool by placing solid blocks (such as sand, stone, or mud) into the water. If the player covers all the blocks of water, then mines the blocks out, there will be no water remaining. This can be a particularly effective means of removing the danger of drowning, especially in subterranean environments. Sand is the most useful resource for this task, as it is pulled down by gravity, and allows the player to fill a whole pool without physically going to the bottom. Another method of doing this safely is to fill entire horizontal sections, starting at the top, a few rows at a time. The player can safely mine a row off the top at a time, and move down the body of water.

This does not work on the 1.1 update, as even if you put a block of dirt, sand, etc... the water will still be there, although if one reloads the game, the water will be gone when you mine the blocks.

Another way to get rid of water is to keep digging down. It is much more dangerous, but if the water flows into a wide enough space, it will effectively be removed. The key is to dig into air pockets that are visible from the pool. By traveling this way, the player can move into areas that may normally be separated by vast tunnels, much in the same way as digging your own tunnels. This technique is more effective underground, though players can use it (by digging very deep shafts) to remove bodies of water on the surface.

There is also a potential glitch that allows for great amounts of water to be cleared quickly; stack a large column of sand in the water as deep as possible, and then use a pickaxe to destroy it from the bottom. For each block of sand that falls, one block of water will also be destroyed. This is because the water quickly rushes to fill the area where the sand is falling, but is then immediately replaced and removed.

There was another glitch that allows bodies of water to be emptied rather quickly. Simply go to the bottom of the water, place 4 blocks down vertically. Next, mine out 3 blocks so that only the uppermost block is still there, then place a door. Now start rapidly opening and closing the door (Breathing Reed increases the time before you need more air). The reason this works is because when you open the door, it removes water that was occupying that space, and when you close the door, more water moves to the missing parts. However, this glitch no longer works.

Some odd behavior can occur when jumping out of water with a Shiny Red Balloon or a combination of Cloud in a Bottle and Flippers. The increased jump height from the Balloon is not considered, and frequently you will not be able to doublejump if you have both Cloud and Flippers equipped.

Several different kinds of blocks do this. A Gravitation Potion that allows you to stand on the brick may cause a similar thing to occur - it is currently untested.

Another glitch is that a grappling hook (vine whip or otherwise) will not attach to some blocks placed in water. This has only been observed with gray brick and glass blocks, though inconsistently. (sand, pearlstone, ebonstone, etc. have been confirmed doing this as well. It is most consistent with sand though.)

Trivia

 * Water does not make Hellstone nor Meteorite blocks safe to walk on.
 * Entering water will cancel the On Fire debuff, but if it is inflicted while the player is already submerged in water (for example through contact with nearby Lava or a Meteor Head it will not be canceled unless the player leaves and re-enters water.