In three portraits, two reprinted from The New Yorker, Wilkinson (Big Sugar, 1989; Moonshine, 1985, etc.) examines the lives of people who earn their living on the water. ``The Blessing of the Fleet'' finds Wilkinson traveling to Provincetown, where for generations Portuguese-Americans have fished the waters off Cape Cod. In ``The Riverkeeper,'' he follows John Cronin, ``the only person in America to list `riverkeeper' on his tax form,'' as he patrols the Hudson. The third portrait, ``The Uncommitted Crime,'' delves into the lives of the Tlingit Indians of Admiralty Island (Alaska), whose culture has been almost completely destroyed by US rule. All three pieces are strong, quietly drawn portraits that derive much of their power from the accumulation of carefully selected facts, some of which are mind- bogglingly strange: Parts of the Hudson River floor, Wilkinson writes, are paved a foot-deep with beer bottles. Wilkinson is a meticulous and thoughtful stylist, capable of grand poetic moments (``All the clouds were swept to the edges of the horizon, as if the sky were a great big dance floor, and you could see the details on the hills and a woman at a window in one of the houses watching us go by''). And he manages to pull the first two portraits together to satisfying resolutions, although ``The Uncommitted Crime,'' while more unusual in subject matter and more ambitious in scope, doesn't work quite as well. Occasionally slow-moving and elusive, it fails to give a solid sense of what modern-day Tlingit life is like. Overall, skillfully wrought, evocative insights into little- known arenas of American life.