Rob, I think you're right. The normal case is good for like 100'. The dive case is good for 320'. Big difference. But why the big flat lense on the dive case but no underwater flat lense to cure the blur?
BTW, the guy who shot the video above has some awesome tips for shooting. I must have watched 50 of them the other day. Seeing his experiements with the GoPro suction mount would have kept me from doing the same with the floaty door. I actually thought it would float the suction mount, but my son found that it didn't. Thank God it stuck to the boat!