From my many years of flying P3s mid ocean, let me suggest to you...
1/ If possible, determine the swell direction from above 2,000 feet.
The direction of the swell will be the overriding factor in the heading you take up for the ditching.
In another era we flew Daks (DC3) on night freight runs Melbourne to Tasmania. For those unfamiliar with the area it meant flying across the Tasman Sea known for its rough weather. Flight planning included obtaining the direction of surface winds and of the primary swell. The idea was to have a planned ditching heading already in your mind in case the impossible happened and a ditching was necessary. Chances were the ditching would be IMC so no hope of observing the waves at the last second when they would be illuminated in the landing lights (if electrical power still available)
This meteorlogical facility is probably still available although I doubt if pilots use it nowadays.