For quick note taking in hostile environments, nothing beats a nice pencil and a Field Notes Expedition notebook.
The expedition is made from synthetic paper, making it waterproof and extremely durable. It’s small enough to keep in a pocket, and tough enough to stay there for months - and if it ever falls out, its high visibility finish makes it easy to spot.
Note, however, that the Expedition’s synthetic paper doesn’t play particularly well with ink - but writing on it with pencil is an absolute, silky, pleasure. For portability, we recommend Kaweco Sport mechanical pencils; for desk use we recommend either Rotring 600s or theprepared.org’s own FSC-certified cedar pencils (paid subscribers only).