I bought this for some through hull fittings on my jon boat.  And to permanently fill some holes in the live wells (the guys before me cut speaker holes in each 40 gallon live well.  I was able to glue a .080" piece of aluminum to the inside of the live well to block the holes.  I used some duct tape to hold the plates in place while this set up, it has a surprisingly long set up time, it was still moldable even a couple hours later.  This means two things, first it's able to flow into all the little cavities if you were using it to fill a fiberglass/wood hole, second it means you have to kind of watch it if you fill a holes that vertical (like I did) because you have to go back and make sure the adhesive hasn't run out of the hole.  It's less viscous than a bathroom caulk but more viscous than a wood glue.