Abstract: An underwater cutting tool for steel, concrete, or the like, comprising a tubular oxygen lance (10) adapted to be connected to an oxygen source (24, 25) and having a pistol grip-like handle (16).Prior to its first use the lance is sealed so as to be ignited safely under water. This seal (12) is adapted to be blasted off or fused by means of an igniter unit (14) which is operable under water, at the same time, firing the oxygen flowing out of the lance (10). The seal (12) preferably is formed by a plug of a material which is easily inflammable or contains such material and hermetically seals the free end of the lance (10).