Swimming: Calories Burned?

taliyai

Hey! If you are a swimmer, or swim a lot with a HRM or simply have an opinion... please respond!

This morning I went to the pool to swim laps. I couldn't find my goggles so in order to keep my head out of the water, I swam laps using a flotation device. I held on to a swimming board and used just my feet to progress down the lanes. I upper body wasn't technically helping me progress. I was simply kicking my feet freestyle, with my arms extended in front of me. After an hour of swimming I timed myself to have been swimming 50 meters in 1m 45s.

What do you think? Was I ---
Swimming laps, freestyle, light/moderate effort -- Calories burned: 395

Or was I ---
Swimming, leisurely, general -- Calories burned: 338

Obviously MFP is showing that the calorie burn is quite close, but I'm just curious as to your opinion. My HRM should be arriving this week, so I will be better off soon.

What do you think?