An apparatus for towing geophysical sources includes a housing; a first geophysical source disposed in the housing so that the first geophysical source is partially exposed to a surrounding environment; and a plurality of ballast tanks coupled to the housing and configured to at least one of: change a buoyancy of the source towing system; and shift a center of mass of the source towing system. A method of towing a geophysical source includes towing a source towing system through a body of water at a towing depth; and operating a plurality of ballast tanks of the source towing system to at least one of: change a buoyancy of the source towing system; and shift a center of mass of the source towing system.