I have a lot of damage on the hull, a little above the water line and below the water line. I am not worried about the the fiberglass work itself cause I have done it on aircraft. I just figured the resin that I will use is different that what you would use on something that would go in the water.depending on what your trying to do, you should be able to get most of your resins at a local autoparts store, I take it your trying to repair somthing in your fiberglass hull on your ski, the really difficult part isn't using the resins and fiberglass patch, its the sanding and then re gel-coating thats hard.
Go to Boat Building and Woodworking Supplies their is lots of information their and products to look at.