[It's a bit of an outburst, but while Momo makes sure his tentacles are out of the way of the snapping claw, he's paying more attention to what the crab is saying. "Water tart" isn't exactly the most charming turn of phrase, but it's a lead of some kind, even though Momo seems more taken aback at an entire other part of this than the crab trying to threaten them.]

Wait, another merperson stole your shell? That's so rude, who does that? [As easygoing as Momo tends to be, other people suffering because of petty unpleasant behaviour is enough to at least make him sound sincerely offended on the crab's behalf. He can't really blame him for being that angry and defensive if that's what happened the last time someone came through.

In any case, he backs off further, arms crossing in a thoughtful sort of posture. Despite the crab's irate attitude, it's clearly washing off his back as he maintains his calm attitude - he's a public figure, so he deals with worse on the regular.]

I think there's been a misunderstanding here. We're not with whoever did that - we're looking for them, though, and if we find them we might be able to get you your shell back. We just need to know which way they went.