How to keep my hair straight after getting my hair wet?

Okay tomorrow at our school were having a Taks Carnival. (I live in Texas so we have the taks test) were going to have a huge tarp thingy covered in baby oil, water, & shaving cream. Well, in the mornings i straighten my hair because god it looks horrible. Puffy, frizzy, Curly BLEH! After my hair gets wet it drys back to the way it was (Curly) Which i hate! How can i keep it straight all day? I don't want to have to bring my hair straightener to school.. Thanks! P.S They're going to have water guns, water hoses, water balloons, etc. so my hair WILL get wet..Thanks:)