You need at least 40 kts on something like a Dauphin for the fin to be effective and by the time you have slammed the collective down and pushed the nose forward, you are already in the water from the height they were at.
Been through these scenarios in the Sea King sim many times and even from 1000' when you know it is coming you are very lucky to survive.
You're right, that you need about 40 Knots for the fin to work.
But with the collective down, the turn rate wouldn't increase further at a high rate and you're in a "controlled" way down, having a slight chance with a flare at the bottom, or arresting the sinkrate with increasing turnrate close to the water, having a less violent crash.
Guessing from the containers on board of the ship, 150 to 200 feet isn't really much height to play with - but still worth a try.
In you don't react fast enough centrifugal forces won't let you do anything
On a typeratingcourse, with just full pedal pushed, I had the opportunity, to see, what effect the right and fast reaction can have against a slow reaction.
Did that from 500 feet with fly away, still having plenty of height left - but you're right, I knew what was coming.
Having a confidental video from a fellow pilot, who needed a total of 500 feet for the recovery to straight and level - pedal still pushed - but going through the video, less than 200 feet were needed to stop the turn and there would have been a chance for a more controlled crash.
SeaKing - or other conventional tail rotors- probably no chance at all from that heights...