Water surface shadow

Ok long story short, I’m trying to create a water surface, i’m using the free “water planes” asset, but when i’m “underwater,” the water surface above me is very dark. From above, it looks just fine, so i need to somehow make light pass through it without affecting the other side, or, which is more probable, to fake another light shining at it from below in the opposite direction. I’m sure many of you have experience with creating water bodies, how have you achieved this? By any of those methods, or is there anything simpler?