Its right against your arm lol. What do you expect?
Set the gps to 1sec update. I bet you have it on ultratrac.
You should probably spend some time on DC rainmaker's website. He's covered both these issues in the past.
it isn't on ultratrc; however, I don't understand how t change the updating time...
I checked the website you suggested but could find only this:
Hands-on: Garmin’s New Descent MK1 Diving Watch
can you post any other link? Thanks!