How to convince your parents to let you quit a sport?

hi:) so i used to do ballet, ice skating, and piano....but i quit them all for who knows wat reason (i was little) :/. and now i swim. i have been swimming since 4th gr. and now im going into 9th gr. and i discovered my new passion for cheerleading(and i mean a true true passion like i practice a lot and i cant stop researching new cheerleading things...im obsessed!) so i was going to do cheer and swimmin for freshman year but i thought i would be in over my head so i dropped the idea of cheer (im still obsessed). for sophomore year i want to do cheerleading and not swimming(i honestly dont like swimming that much anymore)....but my parents wont let me quit it cuz my dad swam and he would get rly mad at me and my mom says i switched sports too much(the sports i quit are mentioned above) and they want me to get a swim scholarship. but my heart is in cheer! how can i convince them to let me switch...again :/. please help! thnx for everything! :)