Wreck diving is recreational diving where the wreckage of ships, aircraft and other artificial structures are explored. Although most wreck dive sites are at shipwrecks, there is an increasing trend to scuttle retired ships to create artificial reef sites. Diving to crashed aircraft can also be considered wreck diving. The recreation of wreck diving makes no distinction as to how the vessel ended up on the bottom. Some wreck diving involves penetration of the wreckage, making a direct ascent to the surface impossible for a part of the dive.

Wreck diving may be divided into three categories of differing hazard and skill and certification requirement:

Non-penetration diving (i.e. swimming over the wreck)

Limited penetration diving, within the "light zone"

Full penetration diving, beyond the "light zone"

The inherent hazards of wreck diving may be aggravated by local circumstances like depth, layout and condition of the wreck, the silting hazard, and general sea conditions such as visibility, illumination, surge and currents, and water temperature. Training for wreck diving may be marketed as an associated service.