The raft’s integrity is the variable that the evidence cannot resolve. It was never found. It could have sunk quickly — a seam failure that allowed air to escape and water to enter — or it could have remained functional long enough for the men to reach shore. The life vests found in the water support the conclusion that the raft was in use at some point: they were not still attached to the men when they were found, which is consistent with the men having discarded them (if they reached shore) or with the vests having come off in the water.
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## The Geography of the Bay at Night
San Francisco Bay is not a uniform body of water. Its currents, depths, and surface conditions vary significantly by location, by time of day, and by phase of the tidal cycle. Understanding the escape requires understanding the specific geography of the northeastern shore of Alcatraz and the waters immediately around it.
The island sits roughly at the center of the bay’s main channel. The Golden Gate — the passage from the bay to the Pacific Ocean — is approximately a mile and a quarter to the west-southwest. Angel Island sits approximately a mile and a half to the north-northwest. The Marin County shoreline is approximately two miles to the north. The San Francisco waterfront is approximately a mile and a quarter to the east-southeast.
The tidal current in the main channel runs both ways depending on the phase. On an incoming tide, water flows from the Pacific through the Golden Gate into the bay. On an outgoing tide, the flow reverses. The transition between these phases — called slack water — is the period of minimum current, when a person or object in the water drifts least strongly in any direction.