Um, Ocean Water is fine. Apple has a workout for open water swim and refers to the ocean in their support page:
https://support.apple.com/en-us/HT205000
Apple warns more about soap water than ocean water. I have done both with my Series 2 SS and had no issues. Swam in the Pacific, in a lake for my first triathlon, and showered with it all the time. It still has no issues and is being passed down to another family member as I replaced it with a Series 3 SS w/LTE
Worth bearing in mind is that this thread (and that reply) is from March 2016, when the original Apple Watch was still being sold (and only marketed as splashproof).
Not quite sure why this thread has been resurrected, I know it's often hard to see post dates, especially on mobile. Would be great if there was a 'This thread is more than X months old' banner at the top, not sure if MR can implement that though.