Evaluation: 
Conclusion: Mariner is not to Water Friendly
Review: I bought this for my husband who is an avid sailor. He had a great experience with it until a little year after the purchase. I thought the battery was dying, but after replacing the battery, the screen was still not clear. I sent it to Suunto. They wanted to charge me $80 to have it repaired because apparently water got into the motherboard of the watch. My husband sails so maybe he had water splash on it on occassion, but he's never swam with it. I find it ridiculous that it's not water resistent enough and that I had to pay for more than the watch is worth to repair it. Needless to say, I would never buy this watch again.
Evaluation:
Conclusion: Excellent features, rugged. A bit big though...
Review: I'm extremely pleased with my Suunto Mariner. It is simply loaded with features that a sailor/racer wil find handy. It can also take a lot of abuse (clumsy me...). There are only two things I can think of where the Suunto Mariner comes up short: First is that it is a bit big when worn on your wrist. However, all Suunto watches are this size; and, once you get used to it, you stop noticing. Although it is big, it is very light in weight. Overall, it is very comfortable to wear. And, the benefit of having a big display is that it is easy to see (and digest) all the data displayed on the unit. Second, many watches coming out from other companies that cater to water-sports enthusiasts include a tide calculator/display. The Suunto Mariner does not have this feature. In my opinion, adding the tide feature would make this watch complete.As it is, however, it is a great watch. In terms of basic timekeeping, it has everything you need. Time, date, dual time, stopwatch, countdown timer, multiple alarms. Accuracy has been perfect over 2 years. It also has an effective backlight display that stays on for a couple of seconds after you push the button - nice.
In sail mode, the main feature is a timer to aid in sail racing. I am just a recreational racer (solings); but I've come to appreciate this feature very much. Essentially, you set it to count down the number of minutes before the final starting gun goes off. As you manoever your boat for position during those 3 minutes (or whaterver), it gives you chime alarms as the time counts down (two beeps when you have 2 minutes left, another 2 beeps when there is 1 minute left, then beeps every ten seconds until the last 10 seconds, then a beep every second, then a final chime). When the final time is reached, the countdown timer switches to a count-up timer. So, it automatically switches to an exact reckoning of your time in the race. There are additional memory and logbook functions that allow you to keep track of multiple races; but I don't use those features much.
The barometer mode is probably less helpful during a race and more so during cruising. It's accurate enough to give you a head's up when a new weather front is moving in. Again, it has memory and logbook functions that are beyond me.
The compass mode is cool, but I don't use it much. It is accurate; but it's easier for me to use the boat's compass than to look down at my wrist. It would be an excellent backup in an emergency however!
I've looked at a few other watches geared towards sailors, and this has been the best of the bunch. Lots of data presented in an easy to digest fashion.
