Yes, this sounds exactly like the kind of explanation you make up on-the-spot when your five-year-old asks, "What makes the fishie puff?" and you just bought her that ice cream cone you told her she couldn't have, and now you can't afford to lose any more credibility. ("But then how does it breathe?" "Through its skin, dear!") The idea that pufferfish hold their breath came in part from observing a species called the Obscure pufferfish, which keeps its gill-flap closed while inflated.