Abstract: An underwater cruise device is disclosed which is mounted to a vessel by a vertical telescoping boom. The device includes a diving chair mounted to the vertical boom which can be selectively submerged during diving operations or completely withdrawn from the water for long distance, surface cruising. A concave, transparent shell canopy is mounted to the diving chair, forming an enclosed upper cavity which can contain a breathable gas ambient to surround the head of the seated diver. Controls are provided on the diving chair to enable the submerged diver to control the extension of the vertical boom into the water and the propulsion and steering of the vessel itself. Radio and television communication with the surface can be provided so that the diver can monitor surface conditions while cruising in the submerged diving chair.