Is there a recessed floor box for a water supply?
My immediate thought for this is a quick connect valve that you normally see in commercial irrigation for remote hose connections.  These are seen outside where a water hose needs to be connected temporarily.  There are two parts - a quick connect valve, and a brass pipe that locks into the valve.  They are sold in the irrigation/automatic sprinkler section of home stores.

 

Link to valve, Link to key

This could be installed in the floor inside of any kind of standard floor box.  These are cheap, and it has few moving parts so it should be pretty maintenance free.  You can connect the hose to the end of the pipe (key), so you don't have to get down on your hands and knees to screw on a hose.  The quick connect only takes a second (literally) to snap in, and you're ready to use your hose.

If its not clear, you lift the black plastic hood of the valve.  The valve is spring loaded.  The key portion inserts into the valve a few inches and you turn in 90 degrees to lock it in place.