My strobes for underwater photography eat batteries up. These cheap, high capacity, rechargeable AA batteries have been great!
I'll generally get 30+ exposures out of a set of disposable batteries, before they start to show visible drop off on the same flash settings as when fresh. With a set of these rechargeable batteries I get nearly twice as many shots, and I'm not throwing them out.
The biggest advantage is I'm changing batteries less frequently on a device that may leak underwater if I'm not careful. What'd usually happen is I take the camera on the first dive, and didn't bother changing batteries. This really screws up my UW photography as I'm typically only figuring out what I want to shoot/do based off the conditions of the first dive. I decided to try some better batteries and they make a huge difference.
I'll assume they work just as well above water.
EBL 16 Pack AA 2800mAh Ni-MH Rechargeable Batteries via Amazon