
As captain of your ship, you are required to go down with her. If you fly Japanese aircraft, the order is a little different (ditch, disembowel, sink, blow up).
The only way I know of to 'survive' a ditching is to end the flight just before the 'blow up and die.' If the plane stops and slowly settles, that's a successful ditching.
Missions can be set to end with a 'successful' ditching (fade to black). There are a couple of 'practice' ditching missions on Netwings.