Answer:
Those who managed to leave the shore either died from exposure or drowned in the cold water surrounding the island
Step-by-step explanation:
The sentence "Those who managed to leave the shore either died from exposure or drowned in the cold water surrounding the island" supports the idea that the location of Alcatraz made escape almost impossible. The waters of the San Francisco Bay surrounding the prison helped prevent escape. The water acted as another line of security for the prison.