Standup paddle board (SUP) and HRMs

I alternate between 1 1/2hour standup paddle sessions and 1 1/2 hour fast walking sessions.
I take along my Sony smartphone and use an App called SpeedView to monitor my speed and distance and time. We walk at an average of 4mph. Depending upon the water and wind conditions, I can also average between 3-4mph on the paddleboard. It feels like ALOT more work than walking.
This morning it was pretty windy and choppy and it was the most challenging paddle session I have done so far. Going into the wind and waves, my average speed was only about 2 mph, but I got up to a max speed of 7 coming back with the wind and waves helping to push me. But when I got done my legs were really burning from all the effort to maintain balance. It's an awesome sport for conditioning and has become my favorite activity. My wife will use the kayak to come with me on rough days, otherwise she enjoys SUP on flat water! We have made a major lifestyle change this past year and now exercise twice a day and try not to let anything get in the way...including weather! We have each lost about 30 lbs and are now just working to maintain our current weight.
Doing all this together with someone is the key. We motivate each other...because there are days when either one of us might feel like just skipping a session. But after the session is over...we ALWAYS feel better and know that it was the right thing to do. And with the help of My Fitness Pal, we track our meals and reward ourselves when we have earned a little "extra"! We have new clothes now, because nothing would fit after losing the weight ! We HAVE to stay in shape now, can't afford to go out and buy any more clothes!

I am now paddling with a Garmin 78sc mounted on my paddleboard and I link it with the Garmin Premium Heart Rate Monitor. I also carry my smartphone and have the endomondo app running and it also records hr along with speed, distance etc. So while paddling, I monitor average speed, distance and heart rate from my gps and then later review and save the trip statistics in Endomondo. So far it is all working great and it makes working out even more fun.
Just as an example, last Thursday I paddled a distance of 4.96 miles at an average speed of 4.25mph and had an average heart rate of 137 bmp and burned 972 kcal. My max heart rate was 148.
I then log in at My Fitness Pal and manually put in 972 calories burned in 70 minutes of "kayaking" (since they do not yet have a category for SUP). The Garmin 78sc floats and is waterproof. My Sony Experia Z3 is also waterproof, but I put it in a zip lock bag and then in a fanny pack. If I do fall in it should not get very wet, if at all !
I use a a Ram suction cup mount for the Garmin and so far it works great. The only thing I am missing is stroke rate and distance per stroke. One of these days I would imagine that Garmin will come up with an Ant+ sensor for that .......

The polar A300 with H7 sensor is waterproof