You can fill it with a filler. Bondo brand filler is widely available in the US (used predominantly in the automotive industry) .. but they do make a marine version of it (although I'm not sure if the "marine" version actually has anything extra in it other than cost). The Bondo brand fillers are based on a polyester resin - so they work just great with gel coats. They even have a light weight version - thought I haven't used the light weight stuff for anything other than r/c boat repair.

Basically you fill in the void with the bondo and sand it smooth (see the other thread about long boards). Spray gelcoat on top, sand, wetsand, polish, and buff and the indentation is gone.

This was a nasty delaminated spot with a big rock dragging dent next to it - I had to reglass the delaminated spot and fill around it to get things smooth again. More during last March at http://www.teamseacats.com/2006/03/




not wetsanded yet: