If boats didn't float, they wouldn't be boats, they'd be anchors.
The boats displace water in such a way that they remain afloat. Hence why most boats have a V hull shape. This allows them to displace the water and remain afloat, if on the other hand you put to much in a boat it will eventually sink.
Boats float because of the principle of buoyancy. The weight of the boat is evenly distributed across its hull, displacing an amount of water equal to its weight. This creates an upward force, known as buoyant force, that is greater than the weight of the boat, allowing it to float.
You calculate the volume of water displaced (volume of hull up to the waterline level), and multiply by the density of the water in which it will float.
The main body of the boat.
the hull helps keep the boat stable, if there was no hull, the boat would go in different directions
You can learn how to repair hull holes in fiberglass boats here: http://www.boatus.com/boattech/casey/17.htm
They float.
Science is what can explain how boats float and work.
A big ship made of iron can float due to its shape and displacement. When a ship is designed with a hull that displaces enough water, it creates buoyant force greater than its weight, allowing it to float. Additionally, the weight of the iron ship is distributed over a large surface area, decreasing the pressure exerted on the water and helping it to stay afloat.
Cracks in the hull
get on a plane quicker