the B737; rear doors remain closed in a ditching and evacuate through overwing and fwd doors.
As said previously, not on all variants. Earlier models were shorter and therefore it was tested that the rear doors were not under water level. -300 and -400 models use fwd & rear doors in a ditch. Later ones such as the - 700 and -800 do not use rear doors. Guessing the same with - 900s as they are longer still.
I noticed in photos that not all - 900s have the extra exit rear of the wing. Is this an optional thing, and is there a crew member seated there, or is it a 'pax briefed/operated' exit, like the o/wings??