Shoutout to my aunt in Galveston who saved her great-uncle's gumbo recipe from a hurricane flood in 2008.
The week after the storm, we found the waterlogged box of family recipes, and she spent three days carefully drying and copying each one by hand before the ink faded completely.
That "free" digital backup isn't really free if you don't already own a scanner. A lot of people don't have one just sitting around. The waterproof container idea is still the more solid first step.