I wouldn't take any of the time lines quoted too literally. For the swimmers who "stayed near the SAR datum/sinking location an hour", this would be accurate only if they checked their watch and kept good notes. It is entirely possible that for those under stress it seemed like an hour, but it could easily have been much less. Likewise for the rescue, you are assuming that the authorities heard the Mayday call directly from the captain (not relayed via other boaters), and that there was no time lag to find an available boat and dispatch it to the location. We also shouldn't assume that a hurried Mayday location was entirely accurate, or that it didn't get garbled in transmission.

There is often a good deal of confusion in these situations.