A ship won't sink if the density of the ship (metal, wood, cargo, any included air) is less than the density of water.
It's possible that a ship of steel will not sink as well. But if it will sink, it would be because the density of steel is greater then the density of water, while air's density is lower then water's.
A ship's draft, or how deep it sits in the water, is determined by factors like the ship's weight, buoyancy, and the density of the water. The deeper the draft, the lower the ship sits in the water. The ship will sink until it displaces an amount of water equal to its weight, which is known as the principle of buoyancy.
If a ship has no buoyancy, then it will sink. In the tragedy of the RMS Titanic, the ship sank due to a collision with an iceberg, which ripped through the underside of the boat. Also the fact that they were going at an incredibly slow speed.
a hole.
The air (within the ship) is less dense than water.,
The ship will sink slightly. Salt water is denser there for heavy objects will float more in it. When the ship goes back to fresh water the density decreases and the ship lowers again. This link gives extra information and some simple experiments for you to try at home. http://www.kidsgen.com/school_projects/how_ships_float.htm
The salt makes the water dense and the object must be heavier like metal or a ship to sink.
To purposely sink a ship is to 'scuttle' the ship.
A stone sinks in water because it is denser than water, causing it to displace the water it occupies and ultimately sink. A ship, on the other hand, is designed to have a shape that displaces enough water to create buoyancy, allowing it to float on the surface rather than sink.
The ship is designed to be buoyant in the water. Buoyancy works when the water displaced by the object becomes equal to the force it is putting on the water
A hole. A hole in the ship's hull can cause it to take on water and eventually sink, even though the hole itself has no weight.