The subject of the present invention is a watertight fire door for closing an opening in a building or edifice comprising, on the one hand, a fixed frame and at least one opening leaf and, on the other hand, sealing means that provide sealing between the fixed frame and the opening leaf when the door is closed. The or each opening leaf comprises, on the one hand, a framework surrounding an empty space capable of accepting or forming a thermal insulator and being sandwiched between two layers and of thermal insulation each essentially produced from a material having low thermal conductivity or diffusivity and, on the other hand, if appropriate, at least one thermal break.