Mathematically, sixths (50 cf) on a set of 108's with a .65 sac rate at a swim rate of 50fpm should get one 1125 feet into a cave on an average dive at Ginnie using an average depth of 78ish feet.

In reality, an intro diver probably will have a .8 sac rate, not know how to work the flow, and swim faster... and not make it nearly as far.

They don't know the secret... The slower you go the farther you'll get