On-duty time doesn’t include time spent on a ferry, unless you’re working while you’re on it (for example, when a bus driver is selling tickets). Note, however, that if you are taking the ferry to travel to your employer where you’ll start driving, this will be considered on-duty time if (a) your employer asked you to make the trip and (b) you will not have taken eight consecutive hours of off-duty time immediately before you start your driving time.