Hawaii, wonderful diving !!
To add to the other great suggestions, might be worth looking into Mares new 'puck' range of dive computers, small and easy to use, really good cost, under $200 on Amazon.
Features:
RGBM (Reduced Gradient Bubble Model)-algorithm
Full Function Air/Nitrox Dive Computer
Precautionary Program Settings
Nitrox Programmable (21-50%)
Ascent rate indicator
Diver-replaceable batteries
Fresh and salt water
Powerful backlight
Air/Nitrox/Bottom timer modes
Nitrogen bar graph
Audible alarms
Temperature Display
Automatic Altitude Adjustable
DEPTH: 492 feet
Computer user changeable Imperial/Metric
Dive Log: 38 hours/50 dives
http://www.mares.com/news.php?id=769®ion=eu