Eight people were rescued from a boat in Boston Harbor on Thursday night when their boat began taking on water, police said. The boaters were by Castle Island when they called for help at 10:57 p.m., said Boston police spokeswoman Neva Coakley. It was not clear why the vessel began taking on water. The eight people ranged in age from mid-teens to 70s, Coakley said. No one was injured and the boat was towed to shore, she said.