What action should a diver take if they lose their buddy during a night dive?

When a diver loses their buddy during a night dive, using a whistle or signaling device to call for them is the most effective action. This method allows the diver to communicate their location and intentions without unnecessarily increasing the distance between themselves and their buddy. Sound is a reliable and immediate way to attract attention in a low-visibility situation, particularly in the darkness of night when visual signals may be ineffective.

Surface immediately and calling for help may place the diver in unnecessary danger, especially if they are far from the boat or shore. Remaining in place assumes the buddy will return quickly and may not be the best approach if the buddy is indeed lost or moving away from the original spot. Moving to a shallower area might alter the diver's location further away from their buddy and complicate the reunion, especially if the buddy was not aware of this change. Therefore, using a signaling device effectively balances safety and communication, maximizing the chances of reuniting with the buddy.