A water-resistant camera has a lens barrel movable toward and away from a fluid-tight camera body for selecting the position of the lens barrel between wide-angle and telephoto positions. The camera has or can be combined with an automatic air-pressure adjusting mechanism for automatically keeping the air pressure in the inner space of the camera at a substantially constant level irrespective of the position of the lens barrel between the wide-angle position and the telephoto position. Therefore, the lens barrel can smoothly be moved with respect to the camera body upon switching between the wide-angle and telephoto positions.