THEY were ankle-deep in sand, busy all over the beaches, clearing the lap-sap - and thrilled to be serving the community. ''They'' were a 100-strong ''Man Yan Bong'' team, led by a gang of young singers, who took the lead recently in the Keep Beaches Clean Campaign, organised by the Urban Council, the Regional Council, the Keep Hong Kong Clean Committee, and Commercial Radio II. The group of energetic artistes included Gigi Lai, Nadia Chan, Angela Pang, Dicky Cheung, Leo Koo, William Tsoi, Vicky Fan and Ian Hung. The message from the singers was that we as Hong Kong citizens should cherish our natural environment and make an effort to keep it clean. The message was later put to music in a ''Keep Beaches Clean Concert'', held at Repulse Bay. It was organised by CRII.