1. AN APPARATUS FOR OBTAINING RELATIVELY UNDISTURBED CORE SAMPLES OF UNDERWATER SEDIMENTS, COMPRISING: AN ELONGATED RECTANGULAR SKELETAL FRAME ADAPTED TO BE LOWERED FROM A SURFACE CRAFT TO THE SEDIMENTS TO BE CORED, SUPPORT MEANS ON SAID FRAME FOR HOLDING THE SAME UPRIGHT ON THE SURFACE OF THE SEDIMENTS, AN AIR MOTOR, HAVING A CASING AND A HAMMER RECIPROCABLE THEREIN, MEANS ATTACHED TO THE CASING OF SAID AIR MOTOR AND SLIDINGLY ENGAGING SAID FRAME FOR SUPPORTING SAID AIR MOTOR FOR LONGITUDINAL SLIDING MOVEMENT IN SAID FRAME, HEAVY WEIGHT MEANS ATTACHED TO THE CASING OF SAID MOTOR, A CORING TUBE HAVING A CORE CUTTER AT ONE END, AND MEANS AT THE OTHER END OF SAID CORING TUBE FOR LOOSELY SUPPORTING THE SAME ON THE CASING OF SAID AIR MOTOR AND FOR RECEIVING THE BLOWS OF THE HAMMER THEREOF, WHEREBY ONLY A NEGLIGIBLE AMOUNT OF VIBRATION IS TRANSMITTED TO SAID CORING TUBE AND TO THE SEDIMENTS BEING CORED.