Mayday has rules converting it's hexes to High Guard range bands.
Going off memory and the JTAS index, there's an article in #22 called Seastrike which deals with using LLB2, High Guard, and Striker underwater. I specifically remember an "X water depth = Y High Guard armor" chart among other things.
JTAS #24 has an article about High Guard/TCS campaigns. Again, IIRC, the article discusses maintenance supplies and other endurance issues along with other stuff I can't quite remember.