Because of the impaired visibility, extra care is needed for night diving. Emergency procedures are not as easy to perform without vision. There is a greater fear at night. For inexperienced divers it is advisable to remain close to the surface, the bottom or some object (e.g. anchor, lines). Free swimming mid-water and without objects to focus on causes apprehension to many divers.
Preferably the site should be familiar, at least in daylight, without excessive currents or water movements and with easy beach access – diving between the boat and the shore. On entry the diver sometimes encounters surface debris that was not obvious from the surface.
Any navigational aid needs to be independently lighted. This includes the boat, the exit, buoys, buddies and so forth. A chemoluminescent glow stick (Cyalume light) should be attached firmly to the tank valve, and at least two reliable torches should be carried. The snorkel should have a fluorescent tip. A compass is usually required. A whistle and a day-night distress flare are sometimes of great value in summoning the boat operator, who has not the same capabilities of detecting divers at night.
Marine creatures are sometimes more difficult to see. Accidents involving submerged stingrays and needle spine sea urchins are more likely.
Signals include a circular torch motion (‘I am OK, how about you?’) or rapid up and down movements (‘something is wrong’). The light should never be shone at a diver’s face because it blinds him or her momentarily. Traditional signals can be given by shining the light onto the signaling hand. Waving a light in an arc, on the surface, is a sign requesting pickup.