I can't help with the GPS but you make me want to share a story.
I came to Ko Tao a never ever diver and stayed for 3 and a half weeks, diving almost every day. Early on, on my 13th dive also at Chumphon; while still struggling to maintain buoyancy and not burn through my air like a house afire I surfaced with the group. Everybody had either a post orgasmic face or tears in their eyes or both. The dive master, a large ex-solider was particularly ecstatic. He asked:
"did you see it?
What?
You didn't see it?
WHAT?
The WHALE SHARK!!!"
Er no. It was during the 3 minute safety stop, I hadn't gotten my prescription lens for my mask and well... I missed it. I didn't feel bad thought because I had no idea what I was missing, and frankly at that point I was still in in love and awestruck with everything I saw.
That evening I spent the money on magnifying lens for my mask to help my lousy eyes. It was money well spent.
Not that I needed an excuse to stay, but I kind of told myself I should stay there until I saw one.
It happened on dives 38 and 39. On the first dive I heard our DM clanking like mad. Since she rarely clanked I paid extra attention and spun around looking in all directions. There were two, swimming slowl and relaxed, tended by a fleet of Remora. They exuded strength and peace. I was told they were teenagers, and they looked to be about 3 meters long. There were only 4 of us and they swam back and forth giving us plenty of time to look, about 20 minutes before it was time to surface.
Soon after, back on the boat, several were spotted close by. About 20 of us jumped in with fins and snorkels and were able to follow. One came right up to the ladder of the boat just to check it out. The next location was canceled and we decided to stay there and dive again when the SI was over.
Back under, it wasn't long till they showed up. I fought the urge to follow, having been told that they tended to go up and down quite a bit. This time there was a scrum of divers, maybe 30 in all (from about 6 dive boats) and the whale sharks kept making passes. Twice one came within less than a meter of me. I was in awe. I could sense their gentleness and curiosity.
Several divers ignored the advice about staying put and we could soon hear dive computer alarms going off. One Japanese diver with a very fancy camera forgot himself and swam into one as he was filming another.
I saw them from every angle, the side, from below, from above, during this 54 minute dive. When I surfaced, I felt like something had happened, something meaningful and significant. But I have no further words for it.
Suffice to say it's part of the reason I am planning my "soft" retirement soon, so I can devote my life to diving.
You are not by any change Karolyn, are you?