US 1549 driven through the streets of Hudson County

[BoeingBoy]

I don't think in the overall scheme of life that the particular makeup of the water underneath 1549 matters except for the extremely good news that the water remained under the Aircraft.

Only that ditching in the ocean involves the swells/waves which make it easier to snag an engine or wingtip first and possibly cartwheel.

The fact that the water at the point of landing was salt water would contribute somewhat to the buoyancy of the A/C if I recall 9th grade science class correctly

You remember correctly - salt water is denser than fresh water (assuming that the Hudson could be considered "fresh"). Which would mean that the fresh water flowing down the Hudson would be in a strata above the salt water in a stable setting. Given tidal effects, ship/boat traffic, and even waves caused by the wind, I doubt that the Hudson has defined fresh and salt water strata though.

Jim