A diving device includes an air pump with a rigid housing including an interior and an opening closed by a sack-shaped flexible part to form a variable pump volume delimited by the housing and the flexible part. The air pump is designed such that if surrounding water causes overpressure, the flexible part is pressed into the interior, thereby reducing the pump volume, and rests against an inner wall of the housing at least partly in a contact section of the interior. The flexible part can be pulled out of the interior against the overpressure by the muscle force of a diver, thereby increasing the pump volume. The air supply line can be releasably secured to a support device, in particular a waist belt of the support device, centrally behind the back of the diver, and a quick ejection device is provided for releasably securing the air supply line.