Has anyone used your (waterproof-moisture protected) cell phone and the Strava app for recording open water swimming? I'm just wondering how the GPS function works at water level. I have a Garmin FR-10...it's waterproof but intended for overland applications, and not designed to operate (correctly) at water level. Consequently the graphic of my swim routes looks like a zigzag, and adds as much as a mile to a two-mile swim.