MFP calories burned -- accurate?

avskk

I've just started working out again after nearly ten sedentary years. I'm mostly doing very gentle, easy things at home (like the Leslie Sansone Walk Away the Pounds videos) because I'm so out of shape and I have an autoimmune disorder that makes movement very painful. I know this isn't going to be a big calorie-burner and I'm mostly okay with that; my intent is to be a little fitter, not to burn a lot of calories.

The other day, though, I went to the pool with my son as my exercise for the day. I was in the water with him for about an hour, just farting around -- showing him how to swim underwater, doing flips, helping him doggy paddle in the deeper areas, doing some underwater "skiing," etc. Just random, fun, easy things. I input this into MFP as "swimming, leisurely" as that was the gentlest/least-intense swimming option... and it told me I had burned nearly 500 calories!

Is this accurate? I really feel like such a low-impact, leisurely activity couldn't possibly have been so effective at calorie-burning. I was starving later and ate back about 60% of those calories, but I don't want to be doing that if I'm not really burning so many. I felt great during and after the swimming -- my joints felt better, I had lots of energy, and I felt refreshed -- so I'm hoping to do it two or three times a week over the summer. I just don't want to eat back way too much if it continues to make me as hungry as it did the other day.

Thanks!

longtimeterp

my hrm says around 500cal for an hour of lap swimming, and i use fins and paddles, so i can imagine thats fairly close...though as a rule b4 i got an hrm, i always took off 10-15% of the suggested burn by mfp