[Nagisa might have scolded Rin for biting on his things, but with as much reverence as he treats oddities like this (such as with his reaction to tearing up the shirt from before), he's not that worried that he'll ruin them just because he can.]

Yup! I've watched 'em collect seashells, but most of the time they just dig the sand up, push it into piles...and then leave it like that for the tide to wash away. It's super weird, but then I tried it...and it's actually kinda fun?