Swimming Intensity: Moderate vs. Vigorous - Calorie Burn Estimation

Question
I found a calculator online that tells you how many calories you burn swimming. You have the choice of vigorous, moderate or light. I'm having a hard time figuring out if I swim "moderately" or "vigorously". I swim about 50 lengths (laps?) in 35-40 minutes. (72 laps is a mile at my pool.) My pool is 25-yards according to their website.What do you think that would be categorized as?  

Answer
Amethyst,
I believe that the level of swimming you are doing is based upon your heart rate and not your yardage.  I would go off of your heart rate or how "out of breath" you are.  This is something that you are going to have to judge.

Being that this is somewhat subjective, you will have to guide yourself.
Eric