Authorities said a 17-year-old boy wearing sweat pants drowned while swimming in an Attleboro apartment complex’s Olympic-size indoor pool on Wednesday. Prosecutors said that New York City resident Ibrahim Iqbal had been swimming for some time at the Crystal Village Apartments, where he was staying with relatives. They said his cousin was nearby but was not swimming. Gregg Miliote, a spokesman for the Bristol district attorney’s office, said Iqbal started swimming to the bottom of the 9-foot deep end, touching the bottom and coming back up for air. The teen’s cousin said he did this several times before failing to come back up. Authorities said the cousin called a building manager and a resident to help pull out Iqbal, who was pronounced dead at a hospital.