Testing the swimming hand finns
Tested these today. I swam the same distance in open water. Yesterday it took me about 11 min. to complete the route and today with the finns it took 7 and a half. So it was quicker and harder as the finns reguire more force and oxygen out of every stroke. It actually felt good. They also make you put more effort to it as you get more speed as well.
Recommended but not mandatory by any means.