Police are investigating the sudden death of a 52-year-old tourist who was helmet diving with her family.Donna Zapata began experiencing breathing difficulties when she was in the Mangrove Bay area of Somerset just after midday on Tuesday. Ms Zapata, who was a passenger on the cruise ship Explorer of the Seas, was helmet diving, which is said to work like a glass turned upside down in water.The diver’s head stays dry in a helmet and there is a constant supply of fresh air pumped from the boat with the excess bubbles flowing out the bottom of the helmet.CPR was given at the scene and Ms Zapata, who was from the US, was rushed to King Edward VII Memorial Hospital by ambulance.However, medics were unable to revive her and an on-call physician at the hospital pronounced her dead at about 1pm.A police spokesman said: “Police have commenced an investigation into the death of an American woman who was visiting the island as a cruise ship passenger. An autopsy will be performed on the deceased during the course of this week.”Bermuda Maritime Operations told The Royal Gazette on Tuesday evening that Ms Zapata had turned blue and had died of a suspected heart attack. Another tourist on a diving excursion also required medical attention and was treated on shore by the ambulance crew.