I was on the swim team at my high school for 3 years and wore a cap to reduce drag and keep my hair in ok condition. I am planning on taking a scuba diving class in my college and was wondering if I should wear a cap or not. Would that be weird or should I do it to not make my hair look like a disaster?

Definitely weird. Possibly ear damaging. You’ll be partially blocking your ears with that cap. They need to be exposed to help you equalize properly. You could experience pain and possible ear damage. That’s why divers don’t use ear plugs.
If you’re worried about your hair getting wet then perhaps scuba isn’t for you? It will happen. It’s unavoidable and scuba isn’t a fashion contest about how your hair looks. It will get wet. It will get windblown.
Edit: Not iffy at all. Cover your ears and you trap an air slug in there that doesn’t reflect ambient water pressure making equalization difficult if not impossible.