Underwater slate, with a special shape that fits to the wrist or forearm and allows place with other instruments without any disturb.

TDS wet notes with 40 waterproof pages and cordura cover with small pockets. Includes graphite pencil.  Allows you to write in and out of the water. It has a loose table marked with a box for run time and to place it in outside pocket with transparent window, so the recorded times can be checked, without opening the book completely.