Boat

A boat is an item and vehicle entity. Boats float and move easily on water, and can be ridden, so they allow fast transportation in Ocean Biomes or any large area of water; however they are quite fragile and easily destroyed by running aground. Boats can be pushed around by water currents, allowing automatic transportation and boat storage, and the use of boats as mechanism components. Notch said that he'll try to make "fancy huge customizable boats."

Once crafted, a boat may be placed anywhere in water, or on land by right-clicking. Breaking a boat with hands/tools yields a boat, while crashing it drops planks and sticks. The player may place boats in lava, but if they try to ride the boat it will break and they will fall into the lava.

Riding boats
Like minecarts, a boat may be right-clicked to enter. However, as of 1.6, boats are exited by pressing the sneak key. Boats can be entered from any direction, including below (which is useful for getting to the surface slightly quicker after diving).

Boats move according to the player's control or water currents. Boats move significantly faster than a player can walk on land or water, but are slower than minecarts. If on land, a boat may still be controlled but extremely slowly.

Boats are controlled by the player's movement keys: they will accelerate slowly in the same direction the player would move if they were not in the boat. As of 1.6.2 boats no longer respond to the strafe and back keys, and can only be controlled by moving forward or by using the forward key to turn it in the direction the player is facing. As a result much of its low-speed maneuverability has been lost, but an effective countermeasure is to look backwards and briefly press the movement key to brake or swerve the boat. As of 1.7.2 (or earlier?), boats respond to the back key. Pushing back turns the boat quickly in the opposite direction the player is facing. When moving fast enough, there will be "water spray" visual effect representing the bow wake.

If you move through an area with only 1 block of air between the water and ceiling, you will take suffocation damage, but can still move anywhere the boat can.

Boat physics
Boats are entities. Boats behave much like off-track minecarts; they can be pushed around slowly on solid blocks, are easily pushed around by water currents, and always face the direction they last moved. The difference, however, is that boats act like solid blocks in that they can sit on top of players, mobs, and other boats, and players, mobs, and items can stand on top of boats.

If a boat runs slowly into another entity such as a player, another boat, or a mob, it will normally bounce off and change direction; however, there is a long-standing bug in Minecraft where running into a mob (or exiting onto a partial block) can instantly kill the player; more details below. Apparently, running into a block will merely stop movement (if the boat does not break). If you crash a boat into another boat, the boat being ridden will be destroyed while the other one will just bump away.

Boats are annoyingly fragile; they take damage by being hit or crashing into blocks at high speed. After taking enough damage over a short interval, the boat will break; if destroyed by your attack it will drop a boat, but if it crashed it will instead drop 3 oak wooden planks (regardless of which type of wooden planks were used to craft it), and two sticks. Although boats are easily broken while travelling horizontally, they do not take damage from falling, thus one can fall great distances in a boat and leave the boat just before it hits the ground to take minimal damage and have the boat intact. Sneaking while on a boat will prevent you from going fast enough to break the boat on impact with a solid block. (This may no longer be possible.) As of 1.3, boats with momentum break thin blocks like lily pads and flat snow, instead of being broken themselves. (This was also when it became possible to get the boat back by breaking it with hand or tools.)

Boats do not break when running into Soul Sand at water level, because Soul Sand has a lower top surface so that the boat merely runs aground rather than crashing, so it is useful to make docks and harbors out of Soul Sand. Though Soul Sand now has the same bug as slabs, when you exit a boat while on Soul Sand, the player will take falling damage, usually enough to cause death.

Doors can be used to control the movement of boats, such as blocking them into docks or preventing them from following a current until the door is opened. This technique is often used to build boat dispensers.

Though boats used to float upward in any type of water, flowing or not, downward flowing water will now cause them to become stuck on the bottom, making many water-elevator devices useless and risking the player drowning. A water elevator constructed solely of source blocks still works, although a bit slower than water elevators before.

As of 1.3.1, Creeper explosions will not disintegrate boats being ridden; rather, the boat will return to its item form and the player will fall into the water. This does not, however, prevent explosion damage to the player.

If a nether portal is constructed so that it has a layer of portal blocks submerged in 1 block deep water, the player can ride a boat into the portal, and the boat will be transported to the nether.

Canals
Canals, consisting of a series of trenches dug on land filled with flowing water, are a possible method of transportation across large distances using boats. A canal transportation system is more time-consuming to construct, but more material-efficient than a rail transportation system. Double doors, fence gates, ladders, pressure plates, dispensers (with water buckets), and sugar canes can be used as consecutive locks on the canal to control the direction of the flow of water in a canal to construct a flowing fully horizontal waterway. Locks can also be used for boat lifts (Water Elevator or Water Ladder) between different elevations of water. (For real life examples, see Wikipedia's canal, lock (water transport), and boat lift.)

It is also possible to construct a canal with still water by strategically placing water in a diagonal line. This makes for faster transportation.

Trivia

 * Boats can be controlled on land, but very slowly.
 * Boats being pushed over snow will make the snow disappear.
 * Boats can be stood on like blocks, and the player will not fall through them.
 * It is possible to get out of a boat and "surf" on it while it is moving, by sprinting forward.
 * On the Xbox 360 version, it was possible to access the Void above the Nether using boats, as of 1.7.3.
 * A crashed boat can be turned into a Wooden Pickaxe or Wooden Axe without leftover materials.
 * Using a Splash Potion of Fire Resistance can cause boats to be immune to fire.
 * When riding a boat through lava without it dying, it will attach to the nearest block and will not be ridden like a boat on water.
 * No matter which type of wood a player uses to craft the boat, a crashed boat will always give oak wood, making it useful to convert wood. By making a boat from e.g. spruce and you want oak, crashing the boat will cause it to break, hence giving oak.
 * Sand, gravel, anvils and dragon eggs drop when they fall onto a boat.
 * If a Skeleton is stacked on top of a boat in water (such as with the /summon command), the boat can be controlled by the Skeleton.
 * If boat is placed on a one thick platform, when it sinks into the ground, going it it will cause you to go through the platform but if you get out you will go back to the top creating a "Ghost Boat" but if you shoot it with a bow the arrow dissapears and the boat breaks w/o dropping an item.

Gallery

 * A video of a simple boat elevator for transportation
 * A video of a boat placed on lava