I think it looks weird.

It doesn't seem strange to me. It would be expected: if there is no light everything should become dark. Maybe it's because you're too used to other ways of representing water.

It is also true that the light calculation is approximate and takes advantage of the simple information that Minecraft provides, and there will always be situations where perhaps there should be more (or less) light.

One thing is true though: in Minecraft 1.12 or below the water looks particularly dark. But it's uncontrollable and it's because the render works differently in that version and later ones.

For me water is looking strange, because other blocks still lighted, when water becomes black losing its colors. And so I get a sense of inconsistency. I think it would be looking better if water had some sort of ambient lighting like other blocks. And thanks you for such an optimised shaderpack.

p. s. I'm not english native, so I can make mistakes.
(I made screenshots using 1.19.4 and iris by the way)