‘Divers do it deeper’ represents a problem with ego trippers and a challenge to adventure seekers. Unfortunately, the competitive element sometimes overrides logic, and divers become enraptured, literally, with the desire to dive deeper. They then move into a dark, eerie world where colours do not penetrate, where small difficulties expand, where safety is farther away and where the leisure of recreational diving is replaced with an intense time urgency.
Beyond the 30-metre limit the effect of narcosis becomes obvious, at least to observers. The gas supply is more rapidly exhausted and the regulator is less efficient. Buoyancy, resulting from wetsuit compression, has become negative, with an inevitable reliance on problematic equipment, such as the buoyancy compensator. The reserve air supply does not last as long, and the buoyancy compensator inflation takes longer and uses more air. Emergency procedures, especially free and buoyant ascents, are more difficult. The decompression tables are less reliable, and ascent rates become more critical.
Overcoming some problems leads to unintended consequences. Heliox (helium-oxygen mixtures) reduces the narcosis of nitrogen, but at the expense of thermal stress, communication and altered decompression obligations. Inadequate gas supplies can be compensated by larger and heavier cylinders, or even by rebreathing equipment, but with many adverse sequelae (see Chapter 62).
Many of the older, independent instructors would qualify recreational divers only to 30 metres. Now, with instructor organizations seeking other ways of separating divers from their dollars, specialty courses may be devised to entice divers to ‘go deep’ before they have adequately mastered the shallows.