The only way to do Currituck to Ocracoke in one day is to start the morning on the Outer Banks in Kitty Hawk or Hatteras. I usally arrive in Buxton or Hatteras late the night before and start out in enough time to catch the 7:00 AM ferry to Ocracoke. Since Ocracoke is just a stop and take photos kinda light I can usally be back at Cape Hatteras Light in time to be in the first group up the light at 9:00 AM. If you are in to climbing and/or the gift shops Hatteras and Currituck can be real time killers.