Advice on filling below the water line

[Dart Eighteen]

I have recently discovered some blistering below the water line on my Achilles. Fortunately, they are mainly just below the water line. I have had the affected areas sand blasted to open the blisters (which are mainly dry) and now need to fill and fare the affected areas.
Does anyone have any advice on what type of filler to use?
I am also unsure whether to epoxy the bottom again or just prime it before I antifoul. She is a fairly old boat and as such has quite a high moisture content in the hull. My thinking is that if I epoxy the bottom, I will just be trapping the moisture.

Any thoughts and advice greatfully received.

 

[mitiempo]

Fill with epoxy thickened with silica.

 

[oldsaltoz]

Epoxy resin resin and closed cell 'Q' Cells, tiny spheres of glass. Waterproof and not too hard to sand.

Also note, any underwater repair should have 2 to 5 coats of epoxy applied wet on tacky.