I see whales all the time. Humpbacks and Minkes. Sometimes a dozen at a time out in chicken canyon. In along the beach when they are feeding on bunker it is a sight to see. I have had them come up right at the boat while drifting live bunker and that always results in a double or triple bite of stripers. 
 
If you didn't hit it, why do you think it caused your list? 
If your fuel tank moved, that was a problem waiting to happen at the next big boat wake.There isn't much room between the stringers for a belly tank to shift that would cause a list. 
 I think you should investigate further and maybe not cloud your thought process with whales. 
 
A list on V20s can be caused by clogged bilge pipe under the tank and clogged pass-thrus in the stringers. Water gets stuck in the space outside the stringer. 
Anyways, not something to take lightly
		 
		
		
		
		
		
		
			
		
		
		
		
		
	
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