Jason Jones and Wade Murphy III raise the sails at dawn on the Rebecca T. Ruark, who, since 1886, has dredged oysters from the Chesapeake Bay of Maryland using only power from the wind. Oysters, once the cornerstone of the regional economy, have declined by more than 98% since colonial times. Despite a recent comeback, the oyster stocks, and the watermen who depend on them, remain threatened by changing temperatures and rising tides. "I've seen more change in the past 10 years than ever," says Captain Wade.