not all fins are created equal. for the mask, fin and snorkel event, does padi specify specify "scuba fins"? if not, try using a pair of swim fins -- shorter, more flexible; and much easier to use on the water's surface. surface of the pool..
I disagree. There are many fins like Mares Quattros or Dacor Tigers that give far more thrust for less effort than short swim fins.
That being said, it really comes down to using equipment with which you are comfortable.