STATE-of-the-art semi-automatic Glock pistols are to replace the standard-issue revolvers used by specialised Marine Police units. The units have already been equipped with modern sub-machine guns, replacing antiquated Sterlings. ''Acquiring suitable firearms for the Marine Police is an ongoing process,'' said Chief Superintendent Spencer Foo Tsun-kong. ''In June, the Sterling, which has been used by the small boat [crews on police launches], Small Boat Unit and Anti-Smuggling Task Force was replaced by the MP5 A5. ''In future, pending approval, revolvers used by small boat [crews] and the Small Boat Unit will be replaced by pistols.'' The Austrian-built Glock, which has a standard 17-round magazine, is made predominantly of plastic and can be fired even with a barrel full of water. The 9-mm pistol, which weighs about 670 grams, is considered by weapons specialists to be one of the best handguns available.