These small craft, all the LCS(M)(3) variant of the Landing Craft, Support (Medium), were intended to attack enemy defences with the craft’s machine guns and mortar from close off-shore. Landing Craft, Support (Medium) mostly had Royal Marine crews, but some had Royal Navy personnel on board too.
Some LCS(M)s also carried artillery Forward Observation Officers (FOOs) who controlled the fire of the self-propelled artillery regiments during the run-in shoot (the guns firing from LCTs as those craft headed for the beach) from as little as 500 yards off the beach: their work was judged to be very effective.
Above: Line drawing of an Landing Craft, Support (Medium)(3). The mortar position can be seen in the bow (at right), with the turret-mounted machineguns to its rear (left). (Image from: Baker, Rowland, ‘Notes on the Development of Landing Craft’ in, Duckworth, A.D. (ed.), Transactions of the Institution of Naval Architects, Vol. 89. (London: Institution of Naval Architects, 1947), pp.218-258.)