Features:

• Shock Resistant, Rust Resistant, 200M Water Resistant
• Auto Dual EL Backlights with Afterglow, Moon Data (moon age of the input data, moon graph),Tide Graph, 12/24 Hour Formats
• World Time, 29 times zones (48 cities), city code display, daylight saving on/off, 3 Multi-function Alarms (1 with snooze)
• Countdown Timer, Measuring unit: 1/10 second, Countdown range: 1 minute to 24 hours,Auto Repeat, 1/100 second stopwatch
• Measuring capacity: 24:59'59.99" , Measuring modes: Elapsed time, split time, 1st-2nd place times, Hourly Time Signal,Button Tone Operation On/Off, Auto Calendar (pre-programmed until the year 2099)

Editor Reviews:

Product Description:
Shock Resistant
Rust Resistant
200M Water Resistant
Auto Dual EL Backlights with Afterglow
Moon Data (moon age of the input data, moon graph)
Tide Graph
World Time
29 times zones (48 cities), city code display, daylight saving on/off
3 Multi-function Alarms (1 with snooze)
Countdown Timer
Measuring unit: 1/10 second
Countdown range: 1 minute to 24 hours
Auto Repeat
1/100 second stopwatch
Measuring capacity: 24:59'59.99"
Measuring modes: Elapsed time, split time, 1st-2nd place times
Hourly Time Signal
Button Tone Operation On/Off
Auto Calendar (pre-programmed until the year 2099)
12/24 Hour Formats
Accuracy: ±15 seconds per month (with no signal calibration)
Battery: CR2025
Approx. battery life: 7 Years
Module 3088
Size of case/total weight
G9100 51.0 x 46.0 x 16.4mm / 53g Size of case / total weight

Amazon.com Product Description:
This Casio men's G-Shock watch is perfect for seafarers; it provides moon data and a tide graph so you'll always know what the tide is. In addition, the digital watch also shows the time in 29 time zones, has three multi-function alarms, a countdown timer, a stopwatch, and auto electroluminescent backlight with Afterglow. The stainless steel case has a dark blue resin bezel that provides shock resistance. A matching blue resin band provides a secure fit and the watch is water resistant to 660 feet (200 meters). It is covered by the manufacturer's 1-year warranty.

Rating : - Nice Watch
Solid watch for those who like a watch on steroids. Functions work well with no issues. Lights up nicely at night. The blue color is unique and breaks the monotony of the normal black style for this watch without being "loud" in color.

Tide function of the Casio watches is the only one I've found you can custom set up by the lunitidal interval for any given area. Granted, it's tricky and requires you to look up the info yourself and put that interval in but the manual does come with a sizeable list intervals of beaches all over the world. If you care to you can program it to your beach based on your local info. A quick search on the web will yield instructions on how to do this.