It seem like I have to replace the alarm battery every few dives on my NA-NEX7. This wasn't the case on my NA-600D. It's basically dead every time I check it?
As to covering your lens on your RX-100 before leaving the water, I believe the RX-100 has a lens protector that covers the lens when you turn the camera off? This is nice because if you have a mirrorless camera like my NEX7, leaving the lens uncovered, especially if you have swing mount diopters mounted, will fry your lens if facing the direct sun. This happened to me at Aquavison dive center in Krabi, Thailand, when the boatman took my rig and laid it on a soft cushioned spot facing directly into the sun for only a few minutes. Apparently the position of the lens coupled with the stacked diopters refocused the sun's rays to the middle of the lens melting the aperture. YES melted and destroyed the lens in very short time. Fortunately, it didn't reach the 24MP sensor! Now I always carry a towel with me and personally instruct the boatman who takes your rig from you how to handle it and making sure it's covered above all else. Assuming a boat handler or dive shop knows what to do with your rig is a big and costly mistake. Most dive shops are photography savvy, but not Aquavision. If you're into photography, stay away from them. They take no responsibility if your rig is damaged. Cover your lens if at all possible before it leaves the water. I'm going to look for some type of lens cover for my Aquatica +10 diopter.