A diving support vessel is a ship that is used as a floating base for professional diving projects.
The ship transports heavy equipment, such as recompression chambers, large quantities of breathing gas supplies, remotely operated vehicles, diving bells and small submarines which need to available and operated at the dive site for long periods.
Cranes are used to lower and raise equipment such as bells and diving cylinders underwater.
The ship may also carry safety equipment, such as a recompression chamber, so that it can act as a platform for a rescue and treatment of divers in the event of an accident.
The divers and the operators of the diving equipment need to be accommodated and fed at the dive site.