Can large aeroplanes (jet engines) actually land in the Sea?
Though it is a theoretical possibility the evidence suggests it won’t work. A 737 (so very small by airliner standards) ditched in a river estuary in 2002 with only one fatality, but that hardly counts. No large, modern airliner has ever landed in blue water without breaking up & suffering very heavy casualties – the example you mention, a B767 is the only example where any number (26%) of occupants walked/swam away, though in this example the casualties may have been lighter if the landing had been more ideal.
The bad news is that very few airliners have been successfully ‘ditched’ in the sea without breaking up and causing massive loss of life. Smacking down on the grass, as happened at LHR recently is one thing, but hitting the sea is the same as hitting solid concrete – it always leads to a break up of the plane and survival rates are very low from such ‘crashes’. http://www.metacafe.