Why Boats float?

A boat stays afloat because its weight is equal to that of the water it displaces. The material of the boat itself may be heavier than water (per volume), but it forms only the outer layer. Inside it is air, which is negligible in weight. But it does add to the volume. The central term here is density, which is mass ('weight') per volume. The mass of the boat (plus contents) as a whole has to be divided by the volume below the waterline. If the boat floats, then that is equal to the density of water (1 kg/l). To the water it is as if there is water there because the average density is the same. If weight is added to the boat, the volume below the waterline will have to increase too, to keep the mass/weight balance equal, so the boat sinks a little to compensate.

Boats

A boat is a craft or vessel designed to float on, and provide transport over, water.

A boat's propulsion can be by propellers, oars, paddles, setting poles, sails, paddlewheels, or water jets. Boats are generally smaller than ships.

Parts of a boat

The roughly horizontal, but cambered structures spanning the hull of the boat are referred to as the "deck". In a ship there are often several, but a boat is unlikely to have more than one. The similar but usually lighter structure which spans a raised cabin is a coach-roof. The "floor" of a cabin is properly known as the sole but is more likely to be called the floor. (A floor is properly, a structural member which ties a frame to the keelson and keel.) The underside of a deck is the deck head.

The vertical surfaces dividing the internal space are "bulkheads". The front of a boat is called the bow or prow. The rear of the boat is called the stern. The right side is starboard and the left side is port. Many boats have a section called the gralper, designed to reduce water flow to the non-hydrodynamic parts of the boat.

Unusual boats have been used for sports purposes - for example, in "bathtub races" which use boats made from bathtubs. Pumpkins have been used as boats as in the annual Pumpkin Boat Race on Lake Otsego in New York state, USA. In this race, very large, hollowed out pumpkin shells are used for boats, powered by canoe paddles.