If windshear was not a factor and the aircraft was serviceable, how else did the aircraft land short of the airfield?
How about an incorrect QNH set putting the aircraft below profile
Crew not visual with the runway due to cloud / rain showers prior to the field
Heavy shower encountered at short final and crew persist with approach
Aircraft flys itself into the water
Only clue of ground / water proximity would come from the rad alt EGPWS calls