Most paints like BC/CCs and linear polyurethanes such as Awlgrip, Imron, Sterling and others are not for constant immersion. It seems most people can put their boats in the water for up to several days without problems but it is not what it stated on the can.
You could go with a regular marine bottom paint such as Petit's Vivid if the boat will be kept in the water for an extended time. Their colors looks sharp and it can stay on a trailered boat indefinitely.
The third option is to re-gelcoat it which most people advise against because of the labor to smooth it out (it is hard to spray it without serious orange peel) though it has been done.
So the bottom line is if you are looking for the best finish and the boat will not be stored in the water, go with an automotive urethane or a linear polyurethane.