Smashing the sea snails aren't picking through shells is wild. Has the author never done beach BBQ? You can cook those guys in their shells for safer eating and pick out the meat with twigs. I hope people aren't mistakenly learning "survival tips" from this manga, they're better off with Dr. Stone. I do appreciate the cute elf though.
All those PET bottles arranged into a solar still for purifying would make sense though. It might be kinda gross, but urine distillation is a survival technique