A documentary about an artist going about his work can be a tedious business, but in “Rivers and Tides” Thomas Riedelsheimer is fortunate in his subject: Andy Goldsworthy, a Scotsman who fashions his sculptures from phenomena of nature–rocks, leaves, branches, flowers, tufts of snow, even (in one memorable scene) icicles. The resultant pieces are mostly ephemeral (one exception being the “clay walls” he fashions for museum interiors), likely to be obliterated shortly by the heat of the sun, the water’s current, the tide, or some other natural occurrence; in some instances they collapse even before they’re finished–and Goldsworthy is left to sit sullenly, staring at the debris. That’s why most are preserved only as photographs that the artist keeps carefully catalogued at home. But in this case some are preserved on moving celluloid, too, and since Riedelsheimer is a careful craftsman, the artist’s creations have a shimmering, evocative, strangely calming beauty.

Goldsworthy is allowed time to describe his methods, too, which–when conjoined to sequences showing him communing with the landscape and collecting the materials to be used in harmony with it–makes for a revealing portrait of his inner life. We come to feel that the works are a perfect expression of the man, capturing his quiet, contemplative nature. It’s not surprising that Goldsworthy is revealed as a solitary individual, seeming peculiarly alone even in the midst of his large, unruly family; his pieces are suffused with a sense of loneliness, too.

“Rivers and Tides” has a soft, ruminative tone, and some viewers may have trouble putting up with its almost mystical reverence for a man who’s effectively making various types of castles in the sand and then watching them dissipate. But if you attune yourself to its wavelength, you’ll find it a lovely, curiously inspiring appreciation of Goldsworthy’s unusual artistic vision.