[Zoro only has one arm free so only one sword...for now. As soon as Luffy's arm flops out of the way, he slashes it out in a simple 36 Pound Cannon to get the creature to back off for a moment]

That's what lives in the lake. That, and a bunch more, and they'd all like nothing more than to make you a tasty morsel.

[there's only a sliver of concern in his tone; after all, these things aren't quite as big as sea kings and geez it's not like they haven't casually punched the shit out of sea kings before. Zoro's less worried about it eating Luffy and more concerned that his captain is seeing things]

C'mon, grab hold of me and let's get back to dry land.