There's been a number of good suggestions for ear wax removal (in the states any drug store has "Debrox" or equivalent). However if he's in pain and he's been doing a lot of swimming/snorkeling it's likely he's got an ear infection which will require an antibiotic. My ENT has prescribed the antibiotic ofloxacin when I've suffered from this. Btw, I also have a prescription for mometasone which is used daily and keeps wax build up under control.