I am not sure what you are saying, but my curiosity was whether the shape or pattern of the light output would change underwater. It is really an academic question, I suppose. I am not sure it could realistically be tested. I was not really talking about the power of the flash.
The shape of the two flashes will be the same however as one is 50% more powerful than the other practically the light at the edges will drop to a value that is considered dark before the other one pretty much of a factor of 1.5 or 0.67x depending in which one is the reference
Underwater or land makes no difference in relative terms but in absolute terms underwater the distance will be shorter due to absorption
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