Escaping from Alcatraz was particularly difficult due to the treacherous waters surrounding the island. The San Francisco Bay is known for its cold temperatures, often dipping below 55°F, which could quickly cause hypothermia and exhaustion. The strong tidal currents were another significant obstacle, making swimming or using a raft perilous. The distance to the mainland was over a mile, and many escapees underestimated the power of the currents, which could easily carry them off course or out to sea. These natural barriers made escape attempts from Alcatraz extraordinarily dangerous and highly unlikely to succeed.