My first, brief, dive to 135 feet (41m) was in 1976 off the coast of Cozumel. I was in a group led by a dive master and we quickly descended, swam through a large ring shaped coral structure at around 135ft, and started our ascent. More accurately, all but one of use started our ascent.

Back then, of course, we had to rely on the Navy dive tables for maximum safe bottom time (just 10 min from entry at the surface to start of final assent), and we still added about 5 minutes at 15 feet as a safety stop before exiting the water. These limits, determined by the Navy for Navy divers are intended to prevent decompression sickness (the "bends").

Unrelated to the bends is another hazard, nitrogen narcosis that can interfere with clear thinking. It usually starts to affect people at around 150 feet and I barely noticed it at 135ft. However one diver in the group was affected and after passing through the coral archway continued to swim down the wall of coral toward the bottom at least 100ft deeper. The dive leader had to chase this diver, catch him, and then go though a real decompression stop or two with him on the way up.

Now days, sport divers can explore these depths more safely by using a mix of nitrogen and oxygen called Nitrox which is a 65/35 percent mix of Nitrogen/Oxygen vs the atmospheric proportions of 78/21 percent. This lowers the partial pressure of Nitrogen while diving and thus allows safe diving at greater depths and duration for sport divers.

If the research described by the featured article is true, this suggest a simple performance enhancer. Perhaps in the future, SAT exams will have to outlaw the use of Nitrox SCUBA tanks in the exam room.