One difficulty of kayak navigation is not having a place to note down departure times, bearings, fixes, etc.
A grease pencil on the deck works to a degree, but it's too clumsy to write much before you run out of deck room.
Then today I discovered that if you wet-sand a patch of deck with #600 sandpaper, it makes a surface that takes ordinary #2 pencil beautifully, even sopping wet, and it erases with equal ease. It might not work too well on a black deck, but any light to medium shade should show up the notations just fine.
So this afternoon I masked and sanded a couple patches of deck either side of my cockpit coaming, so now all I have to do is remember to bring a pencil!
Rob