PADI requires that you be able to swim using any stroke, nonstop, 200 yards without aids of any kind, or, as an option, 300 yards using only a mask, snorkel and fins. Wet suits are not allowed. You cannot swim a couple of laps and stop to rest or the task must be repeated. I think probably the no refund on the boat trip would be if you cancelled, not being told to repeat. With that said, you are not the first, nor will you be the last to have difficulty with the watermanship skills. However, once you are certified and surface with a strong current between you and the boat or shore you will understand why the skill is necessary. I concur with taking some swimming lessons and giving it another go.