And of course Muromi-san, after going on about how it's only the dumb-dumbs that try to eat inedible stuff, tries to eat Takkun's lure. Again.
And you know... it just struck me - Muromi and Levia and the rest of the mermaids actually make sense. They're apparently effectively immortal, so they survive no matter how stupid the things they do might be, so they do stupid things because they don't have any reason not to. They've never had to learn to not be stupid, because they're going to survive anyway.