Wreck diving is recreational diving where the wreckage of ships, aircraft and other artificial structures are explored. The term is used mainly by recreational and technical divers. Professional divers, when diving on a shipwreck, generally refer to the specific task, such as salvage work, accident investigation or archaeological survey. 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.

The environment of wreck diving is sunken shipwrecks and other vehicles and structures, either sunk by misfortune, acts of war, or intentionally, as targets in military exercises, to serve as artificial reefs, or as recreational dive sites for the diving tourism industry. Wrecks sunk as tourist dive sites are usually cleaned up and have many hazards removed before scuttling, and are usually sunk in a place where the other natural hazards are not too serious. Wrecks sunk through misadventure tend to be in places with a wider range of environmental hazards, in many cases contributing to the wrecking event. In many cases the wreck itself presents a range of hazrds, such as entanglement, sharp edged metal plating, disorienting interiors, unstable structure and loose silt deposits.

A shipwreck may be attractive to divers for several reasons:

In The Advanced Wreck Diving Handbook, Gary Gentile sub-divides wreck diving into three categories:

Each subsequent level involves additional hazards and greater risk, and therefore will normally require additional learning and experience to develop the required competence, and may also require additional equipment and the competence to use it effectively.

Non-penetration wreck diving is the least hazardous form of wreck diving, although divers still need to be aware of the entanglement risks presented by fishing nets and fishing lines which may be snagged to the wreck (wrecks are often popular fishing sites), and the underlying terrain may present greater risk of sharp edges.

Penetration within the light zone presents greater hazards due to overhead and greater proximity of the wreck's structure, but because of the proximity of a visible exit point, and some amount of external light, those hazards are more manageable. However, there is clearly a much greater risk of entanglement and silt out inside of the structure, as well as the requirement to move laterally to a defined exit point before one can surface in the event of an emergency.