Swimming with Apple Watch Series 2 and Fitbit Flex 2

We spend some serious pool time with the two waterproof wearables
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After years of users asking for it, Fitbit finally gave the world its first waterproof fitness tracker by launching the Flex 2. Apple meanwhile decided the Watch Series 2 was the right time to give its smartwatch a more swim-friendly design. But both companies didn't just stop there. They went one step further offering lovers of the sea and the pool the ability to track their swimming performance as well.

Waterproofing is always high on our list of priorities, but clearly it's a lot more difficult than it seems. Fitbit revealed that it encountered Flex 2 production issues making the tracker waterproof. But it pulled it off, and we're glad it did but it has been a long time coming.

Read this: Best swimming trackers reviewed and rated

So how does Fitbit's first swim tracker skills compare to the the one that Apple has packed into the Series 2? We've been spending some time with both in the pool to find out. We'll be adding our thoughts on how they fare for open swim tracking once we've had spent some more time testing them out.

Wearing them in the pool

Swimming with Apple Watch Series 2 and Fitbit Flex 2

If your wearable is not equipped to deal with the rigours of a workout in the water, then it's already failed. It can track all the metrics in the world, but if it feels clunky or unwieldy when you're swimming, it's probably (definitely) going to get ditched. The good news on both fronts is that you won't have any problems like that with the Series 2 or Flex 2.

Read this: Apple and Fitbit waterproofing ratings explained

Once you've paired the Series 2 with a suitably sporty strap, it really is a comfortable swim tracker to wear. We've lived with the smaller 38mm model, and it's light, unobtrusive and does not budge. Unlike the Flex 2, it does have the benefit of a full touchscreen display, but that's inactive once you enter swim tracking mode. It's fine though, because Apple's reliable gesture support means a flick of the wrist will illuminate the screen to let you cast an eye over your performance.

Amazon PA: Fitbit Flex 2

Once you've completed a swim, a twist of the digital crown gives you back control of the touchscreen to pause or end a workout. You'll also initiate the eject water mode, which gets rid of the water through the Watch's speaker. It's a clever way to deal with the potential build up of water inside the device.

The Flex 2 is even slimmer and lighter than the original Flex, which means it barely takes up any wrist space. You don't have the screen, but there is an LED notification display that gives you a quite clear visual indication of how much swim time you've put in. One light equals 10 minutes and so on. Fitbit has vastly improved the clasp on the Flex 2 as well, which means you're not going to need to worry about this falling off. It might be a little trickier to take off afterwards, but it's very secure to wear in the water.

Swimming metrics

Swimming with Apple Watch Series 2 and Fitbit Flex 2

When it comes to what you can actually track in the water there's a more noticeable difference between the two devices. Apple simply offers a lot more than Fitbit in this department.

With the Series 2, whether you head into the Workout app on the Watch or the Activity app on your iPhone, it tracks stroke type, workout duration, active calories, average heart rate, lengths and average pace (broken down by every 100 metres). That's the kind of data you'd normally associate with a dedicated swimming watch.

Fitbit keeps things more simple, recording lengths, workout duration and estimated calorie burn. It simply does not have the sensors on board to deliver what the Apple Watch Series 2 can do. When you put it into perspective of other similarly priced fitness trackers that can offer swim tracking though, it's about the standard we've come to expect. That might actually be enough for casual swimmers who are putting in 20 minute swims as opposed to much longer sessions.

The accuracy test

Swimming with Apple Watch Series 2 and Fitbit Flex 2

Apple Watch Series 2 (left and centre) and Fitbit Flex 2 (right)

As far as giving you data you can rely on, we're impressed from our initial testing with the Series 2 and it's more of the same up against the Flex 2. It's hands down one of the best swim trackers we've used in the pool. The TomTom Spark has been our go-to device for testing accuracy. Swim tracking is not its core feature, but it does have a swim tracking mode that proved very accurate in our big swim tracker test earlier this year.

The screenshots above really tell the story of our experience swimming with the Flex 2 and the Series 2 over the last couple of weeks. While the Flex 2 tended to be a little off on the lap count, the Series 2 was at most one length out from the Spark. When paired against each other there was usually a one two to lap difference whether that was for shorter 20-30 minute sessions or hour long swims.

This may well be to do with the manner in which these two trackers log activity. While you have to manually start tracking a swim session from the Workout app on the Series 2, Fitbit uses its automatic activity recognition technology to work out when you're swimming as long as you are consistently swimming for a set period of time. 10 minutes of swim time should really be the minimum.

Dealing with the data

Swimming with Apple Watch Series 2 and Fitbit Flex 2

When it comes to looking back at the swim data and providing some analysis on performance, both are a bit lacking, but more so the Fitbit. The Flex 2 tags your swim as an exercise activity logged inside the companion app, but there are no insightful graphs or any attempt to put the swimming data to any really meaningful use apart from the impact it's had your daily activity goal. Serious swimmers are just not going to get the depth they crave.

Essential reading: Top Apple Watch tips and tricks

It's a similar story with the Series 2. All of the data lives inside the Activity iPhone app, which you can share in multiple places. There are a few pretty graphs, but no way to export the data to analyse a little more closely. The good news though is unlike the Flex 2, there are dedicated swimming apps including those from Swim.com and MySwimPro that do more with the data. So if you want a meaningful look at your swim sessions, the Apple Watch is the one.

The verdict

So what's it like swimming with the Fitbit Flex 2 and the Apple Watch Series 2? Pretty good, but for very different reasons. With the Series 2, there's the screen to view progress in real time, which the Flex 2 lacks and that can feel a bit of hinderance when you don't really know where you're at during your session. In our testing, the Series 2 also proved more accurate as well. That's not to say we weren't impressed with the Flex 2 too, but it was a little off at times.

The Flex 2 is a more simplified experience (and significantly cheaper), but in terms of comparing it to other dedicated fitness trackers that claim to offer the same automatic swim tracking (we're looking at you Speedo Shine 2), it does offer a more reliable experience and one that lets you focus on putting in those lengths. If you want the accuracy and the depth, go for the Series 2. If you're not obsessed with pools of data but still want those sessions to count towards you quest to get in shape, the Flex 2 is not a bad option either.

TAGGED Fitbit Sport

How we test

Michael Sawh


Michael Sawh has been covering the wearable tech industry since the very first Fitbit landed back in 2011. Previously the resident wearable tech expert at Trusted Reviews, he also marshaled the features section of T3.com.

He also regularly contributed to T3 magazine when they needed someone to talk about fitness trackers, running watches, headphones, tablets, and phones.

Michael writes for GQ, Wired, Coach Mag, Metro, MSN, BBC Focus, Stuff, TechRadar and has made several appearances on the BBC Travel Show to talk all things tech. 

Michael is a lover of all things sports and fitness-tech related, clocking up over 15 marathons and has put in serious hours in the pool all in the name of testing every fitness wearable going. Expect to see him with a minimum of two wearables at any given time.

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