Outhouse:
After looking at the flight data available on line and the noting the point that they turned back to the shore, how close were they to the destination rig?
I was thinking the same and tried to figure it out:
The last flight of the same aircraft on flightaware.com between CYYT and the platform had a duration of 1:15.
They departed at 11:47 Z and declared the emergency at 12:15 Z. That's 27 min, so not even half way before they turned around and flew for another 10 min (or 17nm).
The media reports indicate an airliner saw the aircraft only minutes (expendable statement) after the crash already upside down... did it capsized after a somewhat successful ditching? Maybe the survivor was/will be able to tell; on TV he seemed to be conscious when they loaded him into the ambulance.