HC....if the aircraft rolls over with people inside....the outcome is definitely going to be worse than if it stays upright. There might not be fatalities...but the stress and exposure would cause harm to the occupants.
A controlled ditching....and loading of the rafts directly from the cabin beats hell out of the thing going upside down, cabin filling with water, occupants escaping from underwater, then having to enter the rafts (if at all possible) from the water.
Bondu's point about considering Sea State and Environmental conditions as a limitation to Offshore Flights bears consideration.
There is not a single scheduled Offshore Flight that must be flown when scheduled.....every single one of them could be delayed or cancelled till conditions improve.
When does "inconvenience" trump "Safety"......that is the question that needs to be argued.....not "probability"!