Possible Clues:

• Crosswise, on a boat
• A smile across the length of ship
• Perpendicular to a ship's midline
• Crosswise, to a sailor
• A smile from one side to another on journey?
• Note fish out of river to the side of the boat
• Across the ship there's a smile
• Running across a fish leaving river
• Lincoln, say, gets a motorway directly from port?
• ''If I pursue __ of light . . .'': Einstein