Under water perforating machine

The utility model provides an under water perforating machine, comprising a rotary shaft. The rotary shaft which drives a boring rod rotate is connected with a differential mechanism which is connected with the boring rod with differential feed; the lower end of the boring rod is provided with anand a perforating knife center drill; the rotary shaft and the boring rod are positioned in the casing of the perforating machine; one more sealing ring is provided between the lower end of the boring rod and the casing; the rotary shaft and the differential mechanism are respectively connected with a differential gear connected with a counter. One more sealing ring is provided between the boring rod and the casing, and thus the utility model has high sealing property in the process of under water perforating operation. The advancing and retreating stroke of the boring rod is displayed with the digital format via the differential gear and the counter; the reading is accurate and convenient, overcoming the disadvantage that the generally known scaleplate rod cannot be seen clearly under water with easy misreading. In addition, with the digital displaying counter instead of the scaleplate rod, the height of the complet under water perforating machine which has compact conformation and beautiful appearance is reduced.