I have only got the standard Go Pro not the HD. They are great bits of kit. I have just modified a worksite safety helmet to wear when Scuba diving so I can record the dive. It has lots of holes to allow air to escape and a bungee to keep it on my head. I am doing this to for the following reasons:
a. to look extremely stupid.
b. to record the dive so I can replay to identify bits I may have missed while diving.
c. so Mart from Channel ribs can have a better look at some metal he found.