The closest approximation to Scottish artist Andy Goldsworthy's work that most people ever attempt are sand castles, impermanent structures formed out of a landscape that eventually destroys it. But sand castles, by design, are a playful and innocent expression of darker human impulses, a desire to control nature by shaping it into something unnatural. In Rivers And Tides, a quietly mesmerizing documentary about his unusual "earthworks," Goldsworthy makes delicately mutable sculptures out of icicles, moss, driftwood, leaves, and other deposits from soil and sea. But as often as his art gets swallowed by high tide, it achieves the opposite effect of a sand castle, integrating with its surroundings in such a wholly organic fashion that nature can claim partial authorship. Nature starts and completes his work, first by providing him with the raw materials and later by shaping or illuminating it in ways he couldn't have anticipated. A thoughtful, unpretentious 46-year-old with a rural playground in his native Penpont, Scotland, Goldsworthy narrates Rivers And Tides with clarity and good humor, guiding viewers through an artistic process that seems largely private. Since so much of his work melts, decomposes, or gets swept out to sea, his exhibitions are sometimes limited to still photographs of his creations. By following him around with a movie camera, director Thomas Riedelsheimer provides a new and important window into Goldsworthy's world, because the act of making a piece seems at least as important to him as the finished product. In rejecting the controlled, antiseptic art-school environment, he enters into a running dialogue with the natural world, where he continues to participate in its cycles of life, death, destruction, and rebirth. With lovely musical accompaniment by composer Fred Frith, Riedelsheimer globetrots with his subject as he painstakingly links a serpentine sculpture by chewing icicle pieces in Nova Scotia, adds a remarkable cracked clay wall to a museum in Southern France, and lines a stone wall through the trees in an American park. Along the way, Goldsworthy experiences as many setbacks as triumphs–melting ice, the rising tide, flat stones that repeatedly crumble like a house of cards–but his attitude toward failure is admirably sanguine. To him, the relationship between man and nature is give-and-take: When the sea consumes his intricate driftwood structure, its unraveling has a beauty that transcends mere destruction. At times, Goldsworthy's philosophy edges into fuzzy New Age-isms, but with an ever-widening gulf separating humans from their environment, his work demonstrates the enlightening pleasures of reconnecting.