Alcatraz was not escape-proof, at least not during the military period (1853-1933). The first escape, in 1878, was engineered by a pair of men who stole one of the post's boats and rowed themselves to shore. Other prisoners tried to get off using articles such as a butter vat, a bread-kneading trough, driftwood, logs, planks, a discarded ladder, and other bits of flotsam. Four prisoners secured their release by forging the commander's signature on some release papers which the Army duly processed. They were caught a few days after their "discharge". Two other men took advantage of the 1918 flu epidemic: they donned flu masks and officer uniforms for the boat ride to the Presidio. They, too, were caught several days after their release.
Most escapees took an easier route: they waited to be assigned to a shore detail and simply walked off.
The last recorded attempt by a military prisoner was that of Jack Allen. Allen greased his body and plunged into the bay in June, 1930. He, like Roe and Cole and many others was never seen again and became a myth of possibilities.