Cheers for the info people. Deano, unfortunately, a previous owner has already given the gel coat a few coats of white gloss. I've tried and tried to get it back to the gel coat, but can't get a decent finish.
Body filler is the stuff used on car dents etc, a smooth paste mixed with a hardener, bridging compound usually has an agent in it like glass fibre strands with the filler to bridge a gap like a hole. To fill small holes normal filler would be fine if it's above the waterline. Like Deano said I would go with the Gelcoat filler then paint over to match, or look at West Systems small epoxy repair kit.
"Normal" car body fill is not all that waterproof.... Gell coat filler, epoxy or even polyester resin if you are going to paint.... gell coat filler would be easier to work with.