There really wasn't much more for the merman to do other than keep hidden at the moment. This experience was both terrifying and frustrating for him, but what could he do? 
...maybe fix that discoloration that was keeping his tail slightly visible. That was probably a good idea. It was odd that it was doing that, though; normally he didn't have any trouble with camouflage. Perhaps it had something to do with waking up here? How long had he been asleep, anyway? 

As he tried to match the colors around him once more, Runo thought he noticed something looking around the corner of the hallway that he could still see. A more familiar creature, at least, though he hadn't gotten more than a glimpse of it. Maybe this was the help he needed! Letting the disguise fade for now, he pressed against the glass, hoping to see whatever that had been again.