The GPS in the iPhone uses WiFi hotspots and cell towers. Exactly the same as talking on your phone.
I don't have the ScubaCapsule software, obviously, but as soon as I posted that prior message, I took my iPhone 4 off the charger, put in airplane mode, and turned on Angry Birds. That runs the display (actively, not just a passive image) and the audio. I even turned up the volume all the way to maximise the power usage. Just as an aside, I'm really sick of the Angry Birds song now.
After an hour, I'm at 88%. That means I've got a good 8.5 hours of usage, non-stop, screen lit. Tha seems plenty to me. And if not, I know they offer a combination drybag/solar powered rapid charger on their website.
not exactly, the iPhone use A-GPS (Assisted GPS). It will use all of satellites, cell towers and wi-fi hotspots to try to get the most accurate information as fast as it can.