On the night of June 11, 1962, three inmates escaped Alcatraz aboard a makeshift inflatable raft. They were never seen again and are believed to have died in the frigid waters of San Francisco Bay. But a new computer model using historical tide data indicates they had a narrow time window to make it safely to land.

The prison break—intricately planned and executed by bank robbers Clarence Anglin, John Anglin and Frank Morris—was months in the making. The prisoners used sharpened spoons to dig holes in their cell walls, allowing them to gain entry into an unused service corridor. Leaving behind in their beds dummy heads, fashioned out of toilet paper, soap and hair, the three men climbed to the roof through a ventilation shaft, scaled the prison fence and inflated a raft made from raincoats on the northeastern coast of the island.

Advertisement

Recently, a team of Dutch scientists, using historical tide data replicating conditions in San Francisco Bay that evening, calculated the chances of the prisoners making landfall. The researchers ran multiple simulations, launching 50 virtual rafts every half-hour between 8 pm and 4 am from a range of possible locations on the island. Their computer model also took into account that the three men would paddle the raft, particularly as it got closer to land.

The conclusions? In the earlier part of the evening, the outgoing tide would have swept them out to the ocean, where they would have died of hypothermia. If, on the other hand, they had departed after 1 am, the tide would have pushed them back into the bay, possibly south towards Oakland, past Treasure Island. Here too, they would have spent so much time in the water that they likely would have died.

Advertisement

However, as the BBC reports, the prisoners had one opportunity where they could have survived:

If the trio had left at midnight and had paddled hard to the north, then the strong currents could have worked in their favor.

"If they hit it exactly at midnight, the beautiful thing is that we see that they would have been sucked out towards the Golden Gate Bridge," said Dutch researcher Dr. Rolf Hut.

"But the moment they were close to the Golden Gate would have been the moment the tide reverses.

"And that would give them a moment of slack tide, in which they could have reached marine headlands in the northern site of the Golden Gate Bridge."

Advertisement