A buoyancy engine and compression device having a plurality of rotating flexible chains formed of individual segments, each having a plurality of compressible flotation members engaged thereon. The chains rotate around axises at upper and lower frames. The flotation members are alternately compressed and expanded during rotation around the upper and lower frames during passage through an angled pathway defined by paired planar members in an angled engagement which rotate in time with the chain and engaged flotation members. This alternating compression and expansion may also be utilized as an air compressor. Expanded flotation members circumventing the lower frame produce upward thrust as a function of their dimension and displacement of water. Mechanical energy from the system may be harnessed by conventional mechanical engagement of the rotating flexible chains or segments forming the upper and lower frames.