You can book your ferry tickets to Andros Island from Rafina port in Athens through a platform called Ferryhopper. Ferryhopper is an online service that provides comprehensive information on ferry schedules, connections between different ports, and allows you to compare prices across different ferry operators. With an intuitive interface and easy booking process, it ensures a hassle-free experience for travelers. Remember, all ferries arrive at Gavrio Port on Andros Island.