In this half-rapturous, half-technical volume, MacLeish, former editor of Oceanus magazine at Woods Hole Oceanographic Institute, offers a paean to the Gulf Stream. The great blue god, MacLeish explains early on, is not a stream nor a river, but a gyre, a narrow, high-velocity current that runs a hundred miles off the east coast, circling around the weedy mound of the Sargasso Sea. For three years, MacLeish has explored the Stream in the company of skippers of schooners, oil tankers, container ships, and oceanographic vessels. He has dived under with scientists exploring the flora and fauna--and flown over in military craft looking out for icebergs and weather traps for the unwary. There are, surprisingly, many unknowns: ""We have no theory explaining the dynamics of the Gulf Stream east of Hatteras,"" MacLeish quotes one learned oceanographer. That includes just how the Stream warms Europe, for example. On the other hand, local effects can be strong: chimney storms can arise over the warm Stream core under thunderheads, triggering vicious winds and turbulence that can devastate ships (perhaps contributing to Bermuda Triangle myths). Mingled with the science are historical references to Columbus and earlier seafarers, including the fabled St. Brendan, who would have preceded the Vikings by several centuries. As well, there are the first-person experiences and descriptions--occasionally self-conscious, but often as neat as the simile that has southern turtles riding past New England ""like sleeping commuters gone way beyond their stop."" There's much to commend here, for both the serious skipper and those who like to read about wind, weather, and the deep blue sea.