Greetings:

I recently read some USENET posts concerning scuba navigation boards.
One stated the rather than buying one, it was easy to make one using a
Ritchie compass. Surfing the 'net, I see that Ritchie compasses are
traditionally used on board boats. So I'm curious how well they stand
up being submersed. To what depth can they be used in a scuba
application? Is there a particular model number that is recommened for
scuba use?

I also notice that some models are listed as having a low-light/night
viewing capability. How are they illuminated? By using a light and
battery source (in which case I doubt they are submersibile), or is it
some sort of chemical illuminiation (like tritium on watch dials)....

Your assistance is appreciated!