I realize it was only an hour or two into the game, but still, feels bad. I sent achurch my save file, hopefully he'll fix me up.
As far as I can tell, the room (with glowy centipedes, and a save crystal, and glowy crabs outside) is a dead end - and there were plenty of spikes and scary crabs I had to avoid / shoot down on the way in, so trying to go back is completely unreliable - I just start taking damage without being able to see what's causing it, and I can twirl the mouse around all I want, there's no visual feedback to give any indication of my surroundings. I even tried swapping to energy mode and constantly shooting, as a really bad attempt at sonar, listening to how long it took the shots to hit a wall, but that wasn't any help either.
And let's be honest, the only reason to use multiple save files (or even save points at all) is that there's no good autosave - perhaps the real question is why it doesn't just autosave every time you hit a new zone, or gain a new ability, or whatever. Nothing against Aquaria, it's a fantastic game, but I'm just sayin' - I shouldn't have to make multiple saves just in case I figure out something that the game doesn't expect me to do.