I remember BNOC making a safety film in the early 80s which involved landing an S61 on a lake to demonstrate an evacuation. The aircraft was full of aircrew. The first (32 man) raft went upside down, and punctured on an aerial before it could be used. The second, smaller raft was then successfully used to evacuate, but this punctured on arrival at the shore. The boat engine of the craft which was holding the 61 steady then failed, with a risk of grounding the aircraft on the shore, but it eventually took off safely.
This was all on a nice day on a calm lake, a bit different to a winter's night at sea!