"What's the best heart rate monitoring wearable for swimming?" We get asked that question a lot and there's a bit of confusion about whether waterproofed trackers like the Apple Watch Series 2 or the Garmin Vivoactive HR can actually provide that data in the water like they can on land.
Before we get onto the devices that are best suited for measuring heart rate activity in the swimming pool or the open water, we're going to explain why some trackers and smartwatches that pack heart rate sensors are not equipped for monitoring workout intensity underwater just yet.
Essential reading: Best heart rate monitors and wearables
So here's what you need to know about hitting the pool with heart rate monitoring wearables.
Swimming HRMs explained
We've already touched on the subject of the difference of chest strap vs wrist heart rate debate measuring heart rate from optical sensors like the one you find in the Apple Watch or in a Polar or Garmin sports watch and ECG monitors, which are commonly found inside chest straps.
Read this: Best swim trackers tried and tested
Most optical-based heart rate sensors use a series of green lights that flash against the skin to detect changes in blood volume to generate those beats per minute (BPM) readings. The accuracy of these optical sensors have been debated greatly. That's because there's a number of factors that can potentially affect readings, from skin colour to how tightly the device packing one is worn against the skin. It's why many companies use an accelerometer motion sensor to compensate for the movement of the wrist to ensure reliable readings when you're out running or in the gym.
Water is a pretty big issue in this scenario interrupting the ability for those lights to successfully and consistently flash against the skin to track the data. That's why you're unlikely to get any kind of data that is reliable or of any use. At least from the ones that sit around the wrist.
This is why heart rate monitor chest straps are still considered the most reliable for tracking heart rate in the water, whether they're worn under a swimsuit or exposed. We've picked out below the best ones to try out, plus some non-chest strap alternatives you can buy now and that are in the works.
Best heart rate monitors for swimming
Garmin HRM Swim
The HRM Swim is designed with triathletes in mind and comes in chest strap form as well using the same ECG-style method of tracking your ticker. Slapped with a 5ATM waterproof rating it'll store heart rate data including swim interval heart rate statistics. It's also compatible with a host of Garmin wearables including older devices like the Forerunner 920XT and current models like the Fenix 3. It will also work with the upcoming Fenix 5 series.
Like the Garmin, Polar's chest strap is safe to take a dip in the water and is the one of the most reliable monitors we've used in our testing on land. It also uses an ECG-style sensor that detects the electrical activity of the heart to deliver your BPM readings. It also pairs with Polar devices including the V800 sports watch. Its successor the H10 is on the way as well and offers the same swim-friendly design with the ability to store a single workout.
Suunto smart sensor
Suunto's Smart Sensor is a tiny little Bluetooth Smart heart rate monitor that clips into a chest strap and is able to store heart rate data when you're in the water. If you've got a compatible Suunto sports watch like the Suunto Spartan Sport or to the Suunto Movescount app to review data. At 40g, it's no heavyweight, and it's waterproof to 30m.
If you don't want a chest strap, Bragi's truly wireless earbuds monitor heart rate activity from the ears. You'll be able to see record average heart rate for the last 5 minute interval, current heart rate and view heart rate for the entire workout when you're out of the pool. They also have a built-in MP3 player that works in the water to give give you that extra motivational push.
Wareable verdict: Bragi Dash review
Like Bragi, the Kuai headphones are made for the water up to 3 metres in depth. They also feature a heart rate monitor to accurately measure swimming intensity along with tracking laps, speed, strokes and calories. Unfortunately, despite promising to launch in July 2016, the sporty 'phones are experiencing some technical issues in the production process so still haven't shipped. Hopefully, they'll make them out before the end of the year.
Mark this one as one that's on the way. Moov recently revealed its heart rate reading tracker that sits inside a headband to take BPM readings from the side of the head. That's apparently where the skin is thinner and the blow flow is increased, reduces sensor movement and makes for more reliable readings.
It's already launched the sweatband version but a swimming-friendly one is on the way as well that's held in a small silicone case and will slip into a swimming cap to provide data in the pool or out in the open sea.
Instabeat popped up on crowdfunding site Indiegogo back in 2013 raising over $50,000 to make its swimming monitor a reality. Clipping onto a pair of swimming goggles, the connected device helps you ditch the chest strap by reading heart rate from the temporal artery, that's a major artery in the head. It can then project different coloured lights on the lenses to let you know when you're in a specific heart rate zone. The startup is promising to reveal more details in Spring 2017, so here's hoping it's finally ready for the water.