Divers [RECOMMENDED - SOLUTION]

: While not technically paper, these are the industry standard for quick communication. They are made of white plastic and used with a graphite pencil . You can erase the lead later using a Magic Eraser or a bit of sand.

: These use magnetized grains (similar to an Etch A Sketch) and are very easy to read underwater, though they can be bulkier than standard slates. Diver-Themed Paper Crafts Divers

For creative projects, you can make these "paper" divers and ocean scenes: Underwater Slates & Other Diver Writing Devices : While not technically paper, these are the