British military scuba divers practice their skills

Two men assist a man wearing a scuba suit with his breathing apparatus and heavy helmet; he stands with entire outfit (and a nose clip seen through his face-mask); as an officer looks on, the men are assisted with their flippers; they carry a rubber dinghy / VS a diver is helped over the side of a boat; he gives the thumbs up gesture / the diver swamps through an anti-submarine net / Note: exact day not known