So it seems feasible, if the information we have so far is all correct, that they may have clipped Black Rock during the letdown (debris on the rock that could not have been washed up) and then tried to keep control of the damaged aircraft and elect (or had no choice) to make a water landing.
This landing was clearly a hard one but survivable (at least for a short while) for one of them since you don't get thrown out of the cockpit of an S92 if you are properly strapped in.
The whys and wherefores of the choice of letdown position will only come from the accident investigation but, like so many accidents, it probably won't have one cause but many contributory factors where all the holes in the swiss cheese have lined up.
Lets hope the wreckage and the remaining crew-members can be recovered soon, for the sakes of all involved.