Tom,

Did you look to maybe 'hoist' a floatable object (lifejacket, throwable, etc.) up one of the halyards to give some floatation to the mast? If the boat were spinnaker equiped, getting to the spinnaker halyard would be pretty easy. Otherwise, but not quite as effective, the jib halyard might sufice. 'lower' (raise underwater) the sail and attach the floaty item to the halyard. Then hoist the halyard to bring the item down the mast. Try to right the boat again. Hopefully, if you find yourself in this scenario again, that might help get the boat on it's side so you can start problem solving with regard to draining the mast.