The swim.com app worked well on the Pebble when I first got it and even synced with the iPhone fairly consistently until around May of 2015 when it started bugging out. First the pebble doesnt always track yards accurately when doing strokes other than freestyle and it doesnt log at all when kicking in streamline or with a board. Syncing on the iPhone and with the app no longer works at all and my questions/complaints to swim.com and Pebble have gone unanswered. Dont get the pebble just for swimming if that is your main use and forget about swim.com. Very buggy. Too bad.
Swimmingpsychologist about Swim.com: Swim Tracker