Thermal warming suits for a human occupant of a wet submersible vehicle are described. The thermal warming suits provide a dedicated envelope configured to encase at least a portion of the human occupant in a deformable suit that can be assembled around or donned, as well as be removed, by the occupant or others before or after entry and seating in or on the wet submersible vehicle, while underwater or surfaced. The suits provide a deformable, weight and space (i.e. volume) conscious, collapsible loose fitting perimeter around the occupant. The suits can be used to create a pneumatic barrier around at least a portion of the occupant by using a gas such as air provided from a gas reservoir to force water from the interior of the suit.