How do I get rid of a stupid tan...REALLY QUICKLY?

The other day i went to an athletics competition and got a little bit of a tan line which looks really odd and its really obvious where i was wearing my shorts. Now ive just found out about a pool party that im going to tomorrow and i will look stupid if most of my legs are dark and then there is this pale strip!!! so i need to get rid of it REAL QUICK. please, any help at all will be beneficial!