I suspect the height they dropped in from was a good bit less than 50' - that is a bloody long way to fall and the water will hurt a lot.
We used to deploy RN SAR divers from about 20' which was quite high enough for them.
If they were as high as you say then moving away from the overhead in the event of a single engine failure would be quite easy - standard hover height for SAR Sea King was 50' and you would always go forward and down into the water in the event of an engine failure if not safe OEI in the hover. This was practiced regularly in the simulator or, if you were lucky, on a Canadian lake on the Waterbirds course.
Wessex 3 was a single, Wessex 5 was a twin.