Well, the normal path for water into the boat there is through the packing around the driveshaft, inside the big-ole brass nut just below and out of your picture. That's a normal maintenance item and easily adjusted. Are you sure the water isn't coming in there?
If it's actually coming through some kind of break in the fiberglass, I can't help you. You'll probably have to get someone knowledgeable to decide if the crack is a structural problem, or something simple that a patch of fiberglass and a spot of resin will take care of.
So, I guess, the first problem is finding exactly where the water is coming in.
1998 Maristar 200VRS