TheRedHead:
Get a DiveRITE pencil. The absolute best underwater pencils.
I'm surprised no one has mentioned WetNotes.
A couple of people have, actually.
(and floater mentioned it in post #3, actually)
The DiveRite pencils ROCK, but they also break into many pieces in no time, it seems. Every time I rig up a new one, within a dive or two I have 3 pieces.
I've discovered the BEST solution to the underwater pencil problem: The Pilot Croquis artist's sketching pencil.
http://www.cultpens.com/acatalog/Pilot_Croquis_Artists_Pencils.html
(Note I got mine on eBay for a lot less)
All plastic inside. One moving part, a simple plastic worm drive moves the lead in and out of the protective case. Nothing to rust or corrode. The lead is beefy so it won't break easily, but not fragile like the DiveRite pencils, and it sits safe inside the pencil casing so breaking is not an issue. The barrel is beefy and easy to hold even with gloves on. Just twist the little grey end and the lead comes out, a couple more twists and it pulls safely back in. The 6B lead draws a nice, dark, legible line.
LOVE IT.
I tied an 18" piece of thin bungee (1/8"?) to my wetnotes on one end, tied a figure 8 knot in the other end (just to prevent slippage) and ziptied it to the body of the pencil.
Problem solved.