My Bristol has a seacock on top of the CB trunk aft. You take the plug out of the seacock and screw in a threaded aluminum tube with a large piece of dowel in it. Then you open the seacock and can bang on the end of the dowel to free the CB. Never actually had to do this, but it seemed like an elegant solution provided by the builder. No problem doing it with the boat in the water if need be. Perhaps you have something similar or should install one.
Back in the water in Grenada - with new main and #2 and cockpit canvas (Santa came early). Will spend the winter and early spring in the Caribbean and then head to Bermuda and the northeast US. Still trying to decide if we will bring the boat to Canada, either in 2015 or 2016.