Prom is comin up in abt a mth, im rlly tanned cus of swim what do i do to get rid of it, season ends in a mnth?

prom is coming up in about a month and im on the swim team and i am really tanned, i want my skin to be a little lighter, swim season isnt over until beginings of may, so no exposure to the sun is not an option, what should i do? what sunblock do you guys reccomend?