Scuba diving is a deeply pleasurable sport that requires calm discipline. Without mastery of some important skills—proper descents and ascents, buoyancy control, navigating techniques, the ability to recover without alarm from a flooded face mask or lost breathing regulator—an exciting adventure can turn deadly. A diver must always remain under control, even when unexpected problems crop up. Good divers, like good pilots, monitor their instruments constantly, move with steady economy, and understand that virtually any hazard they encounter can be managed with proper training; both are rewarded with the exhilaration of mastering a strange and wonder-filled environment.

The famous first rule of scuba diving is Keep breathing and never hold your breath; but the second rule, Plan your dive and dive your plan, is almost as important. It can be fully appreciated only after one has actually set out from a boat or shore point for a particular underwater destination, with a fixed supply of air, only to discover how easy it is to become disoriented in the dynamic underwater environment. That’s why beginning divers practice with compasses, swimming rectangular and triangular courses back to their point of origin while noting currents, shadows, sand patterns, and natural references as guides to location and course.

Last December in the Caribbean, my family made our first deep-water dive. Down at 140 feet we discovered a forest of tiny garden eels "growing" from the sandy bottom—looking very much like the inspiration for the witch Ursula’s enslaved souls in Disney’s The Little Mermaid. Everything was muted dark gray by the deep, bluish, light, and the water pressure squashed some of our flexible equipment flat as cardboard. Enjoying these wonders safely required careful control of air consumption (which is much faster at depths than near the surface), monitoring for symptoms of nitrogen narcosis, and a slow, timed ascent to prevent "the bends."

That evening we took our first night dive, along with an instructor. Right from the start, there was trouble. Our lights were not all working well, and even with a good beam of light the first experience of diving in pitch-black water is stressful and disorienting. We had buoyancy control problems, in part due to adding wet suits for warmth, in part due to breathing in a less relaxed, systematic way than usual. Then, about 15 minutes into our exploration of the reef at a depth of 50 feet, disaster struck. Our 15-year-old daughter had the terrifying experience of having her mouthpiece separate from her regulator (evidently due to being hit by another diver’s tank), leaving her without oxygen and feeling an explosion of bubbles about her head from her free-flowing regulator hose, all in the dark waters. Her 13-year-old sister was the nearest diver. Once she appreciated the predicament, she supplied her desperate companion with air from her alternate regulator. In understandable panic, the two ascended rapidly, out of sight to the rest of the group. My wife and I will not soon forget the moment we noticed the girls’ absence, then spied two tiny lights bouncing about in a cloud of bubbles far above us.

The girls turned out to be okay, but confused about what had transpired. After we regrouped at the surface, our instructor eventually declared the dive "out of control" and directed us to swim on the surface for the shore lights off in the distance. Ascending the ladder to the dock, one of us declared she would never again dive at night. We had a family debriefing, which included recognition of the importance of using in an emergency the skills we had learned in theory during our classes. The mental replaying of the evening’s terrifying events kept us lying awake in bed until about 3:00 a.m.

The next day, however, we all resolved to attempt another night dive immediately, and it was a great triumph. Breathing and body control came naturally the second time around. We were escorted throughout by a seven-foot-long tarpon—a beautiful shiny metallic creature whose presence was strangely comforting. We spotted lobsters and shrimp (rarely to be seen in daylight) and watched a spotted moray eel devour a fish whole. For the fun of it, and as an expression of our recovered confidence, we all moved back from the reef at about 70 feet, switched off our lights, and waved our arms about—producing a brilliant display of phytoplankton energy that was sufficient to illuminate the other divers in the inky deep. We navigated accurately and calmly back to the dock, feeling relieved and exuberant.

The diving experience is simultaneously thrilling, relaxing, and fascinating. Your senses are honed, and you concentrate with intense focus. There is intellectual challenge in applying concepts of physics, biology, navigation, and photography. You become aware of your body in new ways, appreciating precision and control. Most of all, diving makes you a good observer. Amidst the astoundingly detailed beauty of the ocean and the complex ecology of the coral reef, you experience much more of your surroundings when you go slowly and look carefully—a lesson for our terrestrial lives, too.