I have been training lately with a swimming HR strap. I will admit it is not the most comfortable thing to swim with but I LOVE DATA!!! Especially when you can see this. The workout from my coach was based varying paces. I did intervals where I swam a negative split (swim the second half faster than the first), followed by swimming 4 X 50 descending (each one faster than the last). It is pretty cool that you can see the effort reflected in my HR data! If you want to see all the data you can click here.