BOSTON — Three people were rescued after their 20-foot boat took on water and sank south of Martha’s Vineyard Saturday. U.S. Coast Guard Sector Southeastern New England received a mayday call at 2:24 p.m. from the operator of the pleasure craft Cynthia Z stating his boat was awash with three people on board. The three men put on their life jackets and entered the water with a hand-held radio....