I use these:
They are made from a cellulo-organic material which is known for its depth compensating properties. Specially designed, these precision writing instruments are of hexagonal cross-section in order to accommodate divers wearing a range of gloves. The active ingredient in the instrument is a polymorph of elemental carbon, specially imported from the country of New Hampshire. Each instrument is coated with a patented substance known as "yellow paint" to allow the instrument to double as a signaling device - either at depth or at the surface. You'll notice that image I've posted above is a purpose-built piece of tech gear; easily identified by the lack of several failure points that are commonly seen in recreation pencils:
Plus, you'll also notice the model I use has no wireless transmitter, no switches to fail, etc.
Now, you may say "But Ray, isn't a pencil a life support system?" And of course you'd be right to ask that question. You'd sound like a bit of an alarmist nut, but you'd be right. Either way, I do worry about redundancy for anything that holds my life in its hands (if it had hands) so I always carry an appropriate backup...
Some folks may opt to carry a SparePencil
TM...
but I believe that something that was originally designed to carry just enough graphite to enable helicopter pilots to write "Oh sh-t!" before drowning has no place in tec diving! That's why in cases where you REALLY need redundancy many recreational divers opt to sling one of THESE as backup...
On the other hand, hard-core tec people like myself will often "dive doubles"...
which are perfect as this configuration allows you to completely isolate one pencil in the event of a "catastrophic" failure...
Whatever backup system you choose ultimately comes down to cost/benefit ratio. Extravagant to own two of these highly specialized graphical communication systems? Perhaps. But I spare no expense when my life is on the line. In fact, I recommend that people don't even buy one of these systems on-line. Sure, LP (LeisurePencil.com) offers their own warranty and lifetime battery replacement, but I like to support my LDS (local dime store) which is an authorized dealer with a factory trained technician on-site. I'm not gonna get caught short before a trip or a big dive and have to send one of these instruments back to the manufacturer for warranty service! And don't make the same mistake I did with my first one. (Don't ask how I know, just trust me... there really
AREN'T any user-serviceable parts inside!)
Sure, I pay a little more from my LDS which charged me MAP pricing (
minimum
actual
pencil pricing) of $3.99 for 2 boxes of 144 (remember the tec diver's mantra "2 gross is one, and 1 gross is none!") but they let me try the system out in the pool before buying it, showed me how to set my rig up, and I know they'll stand behind it if anything goes wrong! So, if you want to spend $8 for one super-duper mechanical pencil feel free...or you can get 588 of the instrument that I entrust my life to.
If anyone's interested I can make up a batch, paint them black, and put little blue
H's on them, however that version is $27.50 each.
:shocked2:
So it comes down the darkness of the lead that you want to use. 
