sfbayswims
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Say what happened; the report adds your plan, the data and its age, and the last errors — nothing personal.
Swim times are predictions, not measurements. The swimmer holds each leg's line at your pace against NOAA's predicted current — crabbing, sprinting to 1:00 /100 m from a short reserve where the line can't be held, and counted as swept when even that fails. Wind is shown but not in the physics; chop, fog and shipping aren't either.
Aquatic Park: the current inside the cove is a model — the Alcatraz station's prediction leaking in with a shelter factor, the tidal fill and drain through the openings, an eddy inside the Opening. San Francisco Bay: NOAA's predictions for 43 current stations blended by distance; between stations it's a smooth blend, not hydrodynamics. The current shown top-right is the one honest number — the Opening (cove) or the Alcatraz station (Bay). ≈ marks a reading from a bundled prediction or a climatology rather than live data; a live reading older than a few hours shows its age. Image and map credits: sources.
Swim with a pilot where your club requires one; the Bay swims cross shipping lanes. You are responsible for your own swim.