Louis, it is possible to raise the mast on a h23 while afloat. I've done it several times when I needed to work on something on top of the mast and did not want to bring the trailer out to the lake. The first thing is, don't try to do it by yourself - the mast has little or no lateral stablity while raising or lowering unless you put together some type of "A" frame to guide it. This is exacerbated by the hull's ability to roll in response to weight shifts (you or others moving about on the boat) when flloating. My wife and I tie a small turning block to the bow pin, then run a jib sheet from the forstay through the block and back to one of the jib winches. You could also tie to the jib halyard, except we that when we ran the halyards to the cockpit, I removed the cleats from the mast. I provide most of the lift, with my wife taking load on the sheet/forestay when I shift position (from the cockpit seats to the cabin top, then forward to just behind the tabernacle). I'm also responsible for keeping the mast from swinging off to the side as I don't want to find out which would give first, the mast base or the tabernacle. I suppose she could grind it up on the winch, but we've never done it that way. Too impatient I guess. Actually, the mast is light enough that its not that hard to lift. As it gets to a higher angle, she can do more of the lifting. Once the mast is at or near vertical I support it while she ties off the sheet with enough slack to let her pin the forestay in place and then pins it.
Preparation, as for any other mast raising, is important. Make sure the upper and lower side stays are loosened, or you'll be fighting them as you raise the mast. Remember, the lowers pull the midsection of the mast backward in counter balance to the effect of the uppers on the swept back spreaders. You also need to remember to loosen the forestay and the backstay (I cheat here - with a split backstay adjuster I don't bother adjusting the backstay turnbuckles anymore).
Once you've got it standing, tune your rig the same as you would on the hard, remembering that if you drop something, its much harder to find. Good luck.
Jim Kolstoe, h23 Kara's Boo