There's no such thing as a water proof watch. The Sony will supposedly be rated IP68, which means it is tested to withstand water immersion to a depth of 6.6 feet for 60 minutes. That does not mean it is tested to endure this many times, over a period of months, nor that it will pass this test while the watch is subjected to any additional pressure such as from moving it around or bumping it against another object.
The minimum water resistance recommended for swimming is a depth rating of 165 feet, for playing sports while swimming or snorkeling, 330 feet, and for scuba diving, 500 feet. In other words, the rating is not an indication of how deep you can actually take the watch during normal usage.