After their boat overturns, friends swim for hours toward safety before being rescued. Coming up the anchor rope after scuba diving with friends off Miami Sunday, Raymond Gill looked toward the surface and knew something was amiss. Instead of the bright white bottom of their boat, a weird dark thing loomed overhead. At first, Gill thought they'd somehow found the wrong boat in the murky 70-foot depths, but as they swam up, the truth became all too clear. ''Oh [blank], that's the boat and it's upside down,'' Gill said Monday, only a few hours after he and seven friends had...