First Time to Okinawa

Hey! Will be visiting Okinawa to join a Cruise in December, but we end up back in Okinawa at the end.

I have visited Tokyo many times so first time heading south, I have 2 Nights before the cruise, then 2 Nights on the return but a total of 3 full days.

Any top tips for a foreigner visiting, what are the must sees, what are the must tries for food, may rent a car but depends on suggestions!

Thanks in advance!