But they are volume limited, though I believe they generally store the towed array sonar in the ballast tanks, so the same thing could be done.<p>More serious problems are the time it would take to extend and retract the buoy, speed limitations while the buoy is being deployed, and noise mitgation on the buoy and cable.<p>Right now, submarines carry disposable communication buoys that can be deployed from depth and sent a pre-recorded message via satellite. Submarines can be alerted to a pending message while at depth through Extremely-Low-Frequency radio communication that can penetrate water, at which point the submarine can move to periscope depth and communicate via satellite without actually surfacing.