A mooring system and method of anchoring a buoyant module (16) in a submerged location in the sea for supporting an underwater structure such as a plurality of acoustical arrays (18) for receiving and transmitting acoustical signals is disclosed. The buoyant module (16) is held in a submerged position by at least one anchor leg or line (46) anchored to the sea floor and of a variable length to permit controlled movement of the module (16) to the sea surface (10) for servicing. The single anchor line (46) is a stretchable line and includes an upper segment (56) formed of a Kevlar material and a lower segment (58) formed of a nylon material. Line 46 may stretch easily for a length of 400 feet, a preferred submerged depth of the module (16). Module (16) includes a constant buoyant material (36) and a source of compressed gas (32) controlled by a remotely actuated valve (40) to provide a variable buoyancy.