"Didn't manage to get a map of this cave, but whatever, I'll be fine. Whoever heard of an otter drowning, anyway?"
Now, very much lost and nearing his breathholding limit, he's regretting not bothering to at least keep track of the way out. The cave's seemingly endless splitting paths are way too complicated for him to even begin to memorize, and the only air he's seen was from him happening to go through the same parts again and find the bubbles that had been forced from his lungs. He'll certainly know of a time an otter drowned, if he doesn't find the way out soon.