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So I suspect there are probably scenarios where a powerful video light can effectively increase the ambient and thus produce an ok result when compared to strobes.
Looking at the two pictures above it is hard to see a big difference but you can tell the video light was used for the right picture. I think that the above picture results were helped out by two things, the water is crystal clear and the video light is "contained" by the environment which allowed it to help elevate the ambient more than most open water scenarios.
I agree with your assessment that it's not a replacement solution; I'd be interested in seeing how well this would work in open water though.
Success in OW, using a VL, also depends on the situation and conditions. The cave environment is easier to repeat a shot multiple times and why we often use it to demonstrate. Conditions in OW, that off camera model strobes are useful, is where a model VL may add to or substitute if needed. Such as shooting a diver with a wreck or reef over hang in the back ground. I'll work on getting pictures to show as an example. Getting side by side comparisons in those conditions is unlikely though as it is much more difficult.
We have heard a few people say that VL's are so powerful now that they can replace strobes. This simply isn't how it is, however they can add to or do the job in a pinch if needed. Especially in what we call a "snap and go" situation where setup and adjusting settings is not optimal or possible. The "what you see is what you get" of VL's can be useful in the right conditions.