If MH370 was ditched then it will be intact on the seabed.
Calm sea, then yes, you could ditch keeping the wings and fuselage intact, but minus engines and flaps. But what are the chances of a calm sea in the open ocean? Flying into the swell would be a huge impact. Even flying boats avoided heavy seas.
And I don't believe a controlled ditching is compatible with a suicide. Suicides like a quick, painless death.