Adventure Islands/Busch Gardens?(FLORIDA)?

Okay so I already have a Busch Gardens pass but I want to know what it would cost to have a one day pass to Adventure Island (added on). I know there is some sort of deal where it's like 15 dollars but I am not sure. So please help! EASY 10 points if you give a helpful answer with a link (preferably) to the site where it says it. Thank you!