Interesting thing about swimming is that you don't get the benefit of continued calorie burn like you do from something like running or biking. The cool water keeps your core temp lower and you don't get the metabolism boost. Muscle confusion seems to be the current trend and from everyone I know who is doing cross-fit type workouts, it does work. My daughter can swim 5000 yards in an hour and half practice, but don't ask her to lift anything heavy as she can't do it. Now that she is twelve, she is going to start some bands based exercises.