A shaggy dog tale with a seafaring slant, focusing on the wistful Captain Jonathan, of the tugboat Santa Maria. Towing the great oceangoing vessels out to harbor, Captain Jonathan entertains visions of what is beyond the breakwater. One morning he makes bold: ``We're not going back today. Let's sail around the world!'' A huzzah goes up from the crew, but Captain Jonathan can't maintain the mood once he's made the decision. Nothing can cheer him: not a big spaghetti dinner, not the cabin boy's drawings, not a race with an ocean liner, not even an exotic port of call. He is homesick, to be sure, but he also feels he is shirking his responsibilities back home. A crisis gives the captain the fix he needs: ``He just wanted to be useful.'' No one would deny Slawski his point—and the charming illustrations compensate mightily—but the long, twisted path to making that point may lose readers along the way. (Picture book. 5-8)