A surface vessel capable of lowering a sealed passenger hull into the water and moving the passenger hull through the water for the purpose of conducting an underwater tour. The vessel is equipped with the means to lower and raise the passenger hull vertically such that the center of buoyancy of the vessel and the center of gravity of the vessel remain aligned relative to the force of gravity. The passenger hull is supplied with fresh air from the surface and expels spent air back to the surface thereby maintaining normal atmospheric pressure within the passenger hull. The vessel contains ballast tanks capable of taking on seawater, when the passenger hull is in a raised position. The water ballast being used to offset the buoyancy of the passenger hull as well as increasing the stability of the vessel, when the passenger hull is in its lowered position. Before resuming normal surface operation seawater is discharged from the ballast tanks, utilizing the buoyancy of the passenger hull, while the passenger hull is still below the water surface and not yet in the fully raised position.