To study small particles in their natural medium (for example, plankton or particles settling in water), it is reasonable to use methods of pulsed underwater holography, which, due to the sufficient resolution and the scene depth, allow one to obtain, during single exposure, information about every particle of the entire volume of the medium studied. We have designed a setup, called a simulator of a submersible holographic camera, which is an autonomous laboratory model of a full sized camera. The simulator is intended for development of the methods of underwater holographic shooting, improvement of the technologies of assembling the camera, adjusting the optical system, recording holograms, loading a photoplate holder, shot changing, maintaining the laser system, and so on. Results of experiments on recording model particles and plankton particles moving in water are presented. The volume under study was about 1 liter (with the length of 500 mm), the resolution is 200 μm. Problems of entering the holographic images into the computer and their numerical processing in order to improve the quality and distinguish the objects' boundaries are discussed.