A dive off England's southwest coast has uncovered a rare Bronze Age sword that spent roughly 3,000 years underwater near Salcombe. A find far older than the shipwrecks the archaeologists set out to study. What happened? Earlier this year, the South West Maritime Archaeological Group, or SWMAG, found the sword while investigating a site that had already produced evidence from 17th-century wrecks as well as much older prehistoric material, accord…