How should I ask this girl to prom?

We have been talking for awhile and she is going to say yes, but I was just looking for some cute ideas of how to ask. I'm in Florida right now for spring break and I was thinking of asking her with seashells in the sand and sending her a picture of it. How does that sound? Should I wait till I get home to ask her or is there something else I can do while I am at the beach? And input is appreciated. Thank you