Slow and flat sounds good, although the decelleration forces will increase exponentially with speed. Besides, I was watching discovery the other night, and this crazy doctor was shooting himself off on a rocket sled, and decellerating with over 50g's. He was ok, apart from a few temporary detatched retina, so I think the moral is to have a good tight seat belt.
The CAA do a good 'safety sense' information book on ditching, which can be downloaded from their website....
Cheers
EA