Suppose I am a super-being. From the outside I look and act exactly like an ordinary human. My flexibility of limbs is the same as that of a human so I can't shape-change or bend my arms unnaturally.
My superpowers are strength, speed and endurance. I can move my arms, hands, fingers as fast as I like. My skin is tough so I won't get burned up.
Assuming I have no equipment and am dressed only in an ordinary (but extra-strong) bathing suit, how fast do I have to flap my arms (and or legs) in order to fly? What is the best kind of motion for flight through the air, swimming or flapping?
I am strong enough and fast enough to perform the required movements continuously for say half an hour.
I am not damaged by the stresses and strains of my efforts.
I am of average weight, height build etc. for a human. From the outside, no one can tell the difference simply by looking.
Gravity and other conditions are Earth-normal for me and I have no powers of levitation apart from what I can achieve by moving my limbs.
I can jump for take-off but I can't cover long distances without flapping. I need to fly and maintain constant height and velocity** for at least half an hour and that would be impractical if I simply jumped.
In case anyone objects that my super-powers require magic. That may be so but all the magic is contained within my body. I can't reach out and change the forces of nature such as gravity. I can only affect what is inside my skin and I can't change my mass.
** I've recently edited the requirement to constant height and velocity for clarity.