PAC Member Korey99 did an experiment with a number of different types of materials for log sheets.
“These are the results of my geocache log sheet durability test. From left to right: a tyvek envelope, tyvek housewrap, rite-in-the-rain, the other side of housewrap, and iGage. The top of each sheet was written on when dry, and the bottom half was when soaked. They were submerged for 60 hours then dried for this picture. Many different pens were used.”