A SUBMARINE IN-SITU NET CLEANER COMPRISING A SKID CHASSIS (1) ADAPTED FOR SMOOTH AND SNARE FREE SLIDING ACROSS THE SURFACE OF SAID NET (2), A BUOYANCY MEANS (3) ASSOCIATED WITH SAID CHASSIS TO PROVIDE SAID CLEANER WITH BUOYANCY, A DRIVING MEANS (4) ADAPTED TO COOPERATE WITH SAID NET (2) AND MANOEUVRE SAID CLEANER ABOUT THE SURFACE OF SAID NET, A PROPULSION MEANS (5) ADAPTED TO PROPEL SAID CLEANER ONTO AND MAINTAIN CONTACT WITH SAID NET (2) AND A CLEANING MEANS (6) ADAPTED TO REMOVE CONTAMINANTS FROM SAID NET INCLUDING MARINE FOULING FROM THE SURFACE OF SAID NET SO AS TO CLEAN SAID NET.