As we have discussed, diving at night makes it more of a challenge to orient yourself underwater. This challenge is easily overcome by putting into practice what you’ve learned about underwater navigation and combine it with your night diving skills.
Diving at night is best done in a location where you have recently dove. This will help you recognize previous reference points and landmarks. However, it’s important to realize that objects underwater often appear differently at night than they do during the day. Shadows, or the lack of appropriate lighting will change the apparent shape or size of an object.
A potential complication that divers of all experience levels may encounter when diving at night is spatial myopia. Spatial myopia is the temporary deterioration in the ability to see long distances, and often presents manifests when diving in wide open areas, with no familiar objects or landmarks in view; for instance, during a night dive while the diver is hovering mid-water. The symptoms of spatial myopia can be exacerbated if the diver becomes anxious or focuses his attention on the water, ultimately resulting in vertigo. Complete disorientation is also a potential consequence. In such situations, it may be difficult for the diver to determine where the surface is located, and may result in an uncontrolled ascent. To alleviate these symptoms, the diver should establish contact with his buddy and if possible, the descent line. If the descent line is not available, the diver should stop, establish neutral buoyancy, breathe normally and observe the direction of his exhaust bubbles, which will indicate the direction of the surface. It may also help the diver to hug himself, by wrapping his arms around his body, and then watching his exhaust bubbles. To help prevent spatial myopia, it’s recommended to look at objects that are near you, such as your gauges, more often than you would on a daytime dive.