The lives of people, snails, waterfowl, and blood flukes are intertwined in the story of "swimmers’ itch," known technically as schistosome dermatitis. It is a scientific detective story which in general was solved some years ago although many details remain to be discovered. Swimmers’ itch is a problem of potential interest to readers of The Explorer because one of its focal points is the upper Great Lakes region. In Michigan, at least, there is some evidence that the number of lakes affected with the problem has increased in recent years, and that the geographic range of the "itch" has been spreading southward. Anyone with an interest in ecology, snails, parasitology, waterfowl, swimming, duck hunting, tourism, economics, public health, pollution, or children may have reason to be concerned–at least indirectly– with swimmers’ itch, and may thus want to learn more about it.