10. Save with the permission of the Queen’s Harbour Master or, in the case of paragraph (c), in an area from time to time designated for such activity by him, no person shall swim on the surface or underwater within—
(a)100 metres of the walls, slipways or boundaries of a Crown Establishment;
(b)150 metres of any of Her Majesty’s vessels; or
(c)any area where anchorage is prohibited.