I recently left the gym in San Francisco and ran into my friend Bob. Bob has competed in (and won) international swimming championships, and he was on his way to swim laps. I told him I'd just done the same thing, in an effort to test the new Apple Watch Nike+ swim tracking features. (Apple Watch Nike+ is the functional equivalent of all Apple Watch Series 2 smartwatches, but it has a proprietary Nike sports band and some different clock faces.)
Using the iOS Workout app on my iPhone, I showed Bob the data the Apple Watch Workout app recorded during my 46-minute swim, including active and total calories burned, total distance in yards, average heart rate, number of laps, and average pace. I showed him my average pace per 100 yards, too. And I showed Bob how the Workout app on the Watch lets you choose three different criteria to focus on during swim exercise: active calories, elapsed time, or total number of yards.
Bob hadn't really been interested in the Apple Watch, but after my impromptu demo, he enthusiastically said, "I'm asking for one for Christmas!"
Swim tracking challenge: Apple Watch Series 2 vs. Fitbit Flex 2
For context, I also showed Bob data Fitbit's Flex 2 captured, which I wore alongside my Apple Watch during the pool workout. The data, as displayed in the Fitbit mobile app, included the number of pool lengths I swam, calories burned per minute, and three "impact on your day" metrics: the number of steps taken (zero, not surprisingly), total calories burned, and total active minutes.
Bob wasn't impressed.
Is it fair to compare a $99 activity tracker (Flex 2) to a $369 or more smartwatch (Apple Watch)? On many levels, no. Their price points and different designs make it clear they aren't meant for the same types of customers. However, Apple and Fitbit announced their first "swim proof" wearables around the same time. (For the record, Fitbit's announcement came first). So a comparison of how the two devices track swim workouts is still relevant.
Something else worth noting is that swim workouts Apple Watch Series 2 or Nike+ edition tracks help you meet your Activity app's three daily goals: Move (for calories burned), Exercise, and Stand. If you share Activity data with friends or coworkers, a swim workout can help you jump ahead.
Flex 2 counts swimming toward the day's active minutes and calories burned, and it records the workouts automatically as exercise. But those metrics don't show up on the Fitbit leaderboard. The device doesn't magically translate swim strokes into steps, which do show up on the leaderboard. In other words, Flex 2's swim workouts won't help you jump ahead of others on your leaderboard.
Apple Watch Series 2 swim workout data isn't perfect
As much as Bob and I appreciate Apple Watch's swim data, it's not flawless. As I swam, for example, the Watch sometimes fell behind by a length, or the distance from one side of the pool to the other. It would catch up, fall behind again, and then catch up. When I completed a workout, the Watch was one pool length behind the actual distance; it registered 59 lengths instead of the 60 I swam.
Other swim-proof wearables can provide more detailed stats, as well. Garmin Swim ($150) tells you the number of strokes you take, stroke type, and your swimming efficiency (known as "swolf"), for instance.
Fitbit Flex 2 or Apple Watch Series 2?
Fitbit's Flex 2 is suitable for people who do a variety of exercises, including swimming. Apple Watch Series 2 and the Nike+ edition are better suited for people who want a smartwatch, who swim frequently and who want to up their game in the pool or ocean. However, hardcore or competitive swimmers will be better off with advanced devices that can provide swolf numbers and other, more detailed stats.