Shipwreck

Shipwrecks in shallow water near busy shipping lanes are often demolished to reduce the danger to other vessels.
Depth, tide and weather
On the seabed, wrecks are slowly broken up by the forces of wave action caused by the weather and currents caused by tides. Also more highly oxygenated water, which promotes corrosion, reduces the strength of ferrous structural materials of the ship. Deeper wrecks are likely to be protected by less exposure to water movement and by lower levels of oxygen in water.