Help with being a marine mammal vet.?

I've always wanted to work with dolphins, so I've decided the best way is to be a marine mammal veterinarian. I am really confused on colleges though. Can someone give me a list on colleges that would be best for this, all the requirements, and as much information as you can? Also, I keep reading about something called pre-vet courses. What is that and is it required? I am really confused so please help!!!!