You are correct about the difficulty of ditching in the ocean. See Admiral Cloudberg's description of ditching a DC-9 in the Caribbean during bad weather. There were many survivors.
Very interesting article. Worth noting that the position and size of the engines on the DC-9 would likely be more favorable for ditching than that of most modern airliners. The low and very large underwing engines generate a huge yaw force as soon as they contact the water, and it's very difficult to get both to contact at exactly the same time in a rough sea.