Ok, I misunderstood the geography of the crossing between Corcyra and Croton. I thought (151,79) was the only safe ocean square on the Croton side of the crossing, and that it might be desirable to form an agreement for the use of that square. Since (151,77) can be reached in 19 moves from the Corcyra side, crossing ships have a choice of three squares to end their turn on.