Honestly, the settings you use will depend on the subject you are shooting. It will take some trial by fire to learn what you like best. My main suggestion is to become very familiar with how to navigate the menus, camera and strobe settings, and manual white balance with the housing on before you take it into the water. That way, you can make your adjustments on the fly without wasting too much time. If you don't feel like messing with most of that, the auto setting does a pretty good job, and you'll learn from there what things you'll want to tweak.
I would just keep the saturation setting at normal. I used to use the "Vivid" setting on the DC1200, but on the DC1400, it seems to saturate blues more than it did before. Granted, this was with a very limited trial on "Vivid", but you can always add a little saturation post-production, if needed.
As far as the battery is concerned, I wouldn't suggest three dives on one battery. As you know, you'll always see the coolest stuff when your battery is D-E-A-D. I can make it through two dives, but that's only because I set the auto-off to it's lowest setting (1 minute), turn off the image stabilization, and keep the LCD screen at it's lowest brightness setting. I highly suggest buying a backup battery and external charger if you haven't already. Also, get rechargeable batteries for the strobes, and charge them overnight every day or so. Better to be safe than sorry, and it'll save you money on batteries in the long run.
Enjoy Roatan! I'll be in Utila in a couple of months and can't wait.
