What defines a decompression dive?

A decompression dive is specifically defined as a dive that exceeds the no-decompression limits, which are the maximum times you can stay at a given depth without needing to perform mandatory decompression stops during ascent to prevent decompression sickness. When divers go beyond these limits, they accumulate nitrogen in their bodies that can require a controlled ascent to safely release this excess gas and avoid potential health risks.

The other options relate to aspects of diving but do not accurately define a decompression dive. Advanced training is important for managing deeper dives but does not itself indicate that a dive is a decompression dive. Cold water conditions may present additional challenges but are unrelated to the idea of decompression limits. Similarly, while a longer dive could potentially involve decompression, not all dives longer than 60 minutes will exceed no-decompression limits, depending on the depth and conditions. Hence, the defining characteristic of a decompression dive is its relation to no-decompression limits.