Puffers are cool fish to swim with, they aren't very afraid of people at all. At this spot (Mismaloya) I could see two or three varieties of puffer at any given moment. The porcupine puffers get pretty huge, up to about two feet long. The Golden puffer was at least 14", bigger than a football.
I've never seen one puff up in the wild, only netting them from an aquarium. I've harassed them before just to see if I could get one to blow up, but they always just swim away...