Just a quick calculation
A gallon of water weighs 8.34 lbs (saltwater weighs even more)
The fuel capacity of AE's Electra was 1151 gallons
1151 x 8.34 = 9,599 lbs of displaced water by the fuel tanks alone.
The weight of the plane was about 7,265 lbs
Crew, cargo and other fluid weights are not known exactly but my guess is if the fuel tanks were not ruptured, crushed or had a leak, and were empty, then this "flying gas tank" should float. Likley nose down, more or less, due to the engines, w/ open front cowl not being very buoyant.