Buoyancy control systems for tubes are described. In one embodiment, a
buoyancy control system can include a composite tube and a buoyancy
control material for controlling the buoyancy of the composite tube. The
composite tube can include an internal liner an external coaxial composite
layer of fibers embedded in a matrix. One or more portions of the buoyancy
control material can be attached to one or more portions of the composite
tube to adjust the buoyancy of the one or more portions of the tube.
