The outer points of the crater rim were the only parts of Da Vinci Island still visible over the water, though they weren’t more than twenty kilometers away. There was an intimacy to a small globe. And the boat was very fast; it hydroplaned in any wind over fifty kilometers an hour, and the hulls had underwater outriggerkeels that extended and set in various dolphinlike shapes, which along with sliding counterbalance weights in the cross struts kept the windward hull in contact with the water, and the leeward hull from driving too far under. So in even moderate winds, like the one striking their unfurled mast sail now, the boat shoved up onto the water and skated over it like an iceboat over ice, moving at a speed just a few percent slower than the wind itself. Looking over the stern Sax could see that a very small percentage of the hulls were actually in contact with the water; it looked like the rudder and the outrigger-keels were the only things that kept them from taking flight. He saw the last bits of Da Vinci Island disappear, under a bouncing serrated horizon no more than four kilometers away from them. He glanced at Ann; she was clutching the rail, looking back at the brilliant white V-tapestries of their wake. Sax said, “Have you been at sea before?” meaning, entirely out of the sight of land.

“No.”

“Ah.”