An embodiment of a submersible warming garment comprises a closed fluid loop including a warming conduit disposed in thermal communication with a chamber containing a catalyst and a cooling conduit disposed within a wearable garment. A pump moves the fluid through the warming conduit, where heat is gained, to the cooling conduit, where heat is surrendered to a human wearing the garment, and back to the pump. An actuated valve on a container of fuel and an actuated valve on a container of oxygen are controlled using a controller to provide a combustible mixture into the chamber where the mixture reacts in the presence of a catalytic member to generate heat and combustion by-products. The combustion by-products, including carbon dioxide and water, are one of adsorbed and absorbed by a carbon dioxide scrubber and a reusable water storage medium. A fan moves the by-products into the scrubber and water storage medium.