Though I have a Suunto Observer (Ti) and a Momentum Pathfinder (technically rated to 100M), I always SCUBA with a Timex Ironman.

Its cheap enough that I prefer buying current models when the battery dies (instead of replacing batteries). I've never had issues so far (though my deepest dive was only between 180-200ft) and I find the alarm the best of all my watches.

Backcountry is often a toss up between the three mentioned, but the attraction in the Ironman, again, is that I don't cry if I scratch it up (or break it). $25-$35 is much easier to swallow.