With regard to SNUBA, there are real concerns. There's always danger breathing compressed air under the water. It is necessary to understand very well, the need to continue to breath and *never* hold your breath. Too quick an ascent from even a *very* shallow depth can be dangerous. Boyles Law applies to SNUBA the same as it does with SCUBA.

A fish and a bird can fall in love, but where will they build their nest?