Howard Fields, 39, is making an outlandish splash in business. Three years ago, the Sausalito, Calif., entrepreneur plunged into the world of exotic- swimming-pool and -pond design. Now he is a leading creator of aquatic fantasies, with about 200 projects to his credit. Among them: a $3 million pool masquerading as a river that flows for the equivalent of six city blocks at a Puerto Rican resort. At Washington's Grand Hyatt Hotel, Fields is working on a $1 million, 3,000-sq.-ft. lake that will feature hundreds of live koi fish, 100-ft. waterfalls and a piano perched on an artificial island.
All that...