Alcatraz Island (/'ælk??træz/) is a small island 1.25 miles (2.01 km) offshore from San Francisco, California, United States.[1] The island was developed in the mid-19th century with facilities for a lighthouse, a military fortification, and a military prison.
In 1934, the island was converted into a federal prison, Alcatraz Federal Penitentiary. The strong currents around the island and cold water temperatures made escape nearly impossible, and the prison became one of the most notorious in American history.[4] The prison closed in 1963, and the island is now a major tourist attraction.
The Alcatraz of the Rockies - Florence houses male inmates in the federal prison system deemed the most dangerous and in need of the tightest control, including prisoners whose escape would pose a serious threat to national security. https://en.wikipedia.org/wiki/ADX_Florence#Function
Drowning would be a too comfortable way for him to go.
"Leavenworth would be a perfect home for him. I think Alcatraz would be better. Perfect, in fact. He'd be easy to protect there, and he couldn't escape, since he apparently doesn't swim."