I agree.
But, they are getting better and better.
Our App dims the display and turns off the image sensor after a while.
Based on our tests a 4S will last ~6 hours and a 5S almost 10.
---------- Post added October 15th, 2014 at 09:21 AM ----------
Have you ever heard about the iDive housing for iPad?
There seems to be quite some interest from the scientific diving community about the possibility to take a tablet underwater to facilitate the diver 's activity.
An excellent step forward for survey work. So much data can be collected with the iPad idive housing. Great stuff.