A knot is 1.69 ft per second. A "good" swimmer "might" be able to swim against a two knot current momentarily, but can't sustain it.
10 ft/second is roughly a 5 kt current, or faster than a brisk walking pace.
I've been on boats while drifting just outside the Golden Gate while watching the GPS on an outgoing tide with high flow from the Sacramento river delta. Highest reading we ever saw was 5.5 kts. The channel marker buoys (the 12-14 ft diameter shipping channel ones) were mostly under water with a wake coming off of them that looked like a wakeboard/ski boat.
I've been in some ripping currents (Coz, Molokini Crater, etc), but after finding some reference point to measure objectively, it seems to be half of what I ever guesstimated.
10 ft/second is roughly a 5 kt current, or faster than a brisk walking pace.
I've been on boats while drifting just outside the Golden Gate while watching the GPS on an outgoing tide with high flow from the Sacramento river delta. Highest reading we ever saw was 5.5 kts. The channel marker buoys (the 12-14 ft diameter shipping channel ones) were mostly under water with a wake coming off of them that looked like a wakeboard/ski boat.
I've been in some ripping currents (Coz, Molokini Crater, etc), but after finding some reference point to measure objectively, it seems to be half of what I ever guesstimated.