This was my second Optimum Time, the big red one packing up after 3 years due to water ingress.
Chose this one as it was less bulky. Loved it for the first few races, worked perfectly once I remembered which button was SYNC as it was different to the big red. Then came our first big capsize, & after a couple of minutes in the water pulling in the gennaker & righting the boat the watch stopped working, buttons not responding to anything.
Second time it got wet was to wash the salt off by popping it in a bowl of water for 30 seconds - this time it gave up totally with half the characters missing & everything freezing. Has now gone back for a refund & sadly will not be replaced (really missed it sailing this weekend, will have to find something else less challenged by getting wet).
Great watch for what it does, but waterproof, not in my experience.