Unlike the Java Edition, the amount of light seen by the player underwater changes globally as (s)he ascends or descends. For instance, they go underwater, see a lit ocean floor, they descend, and all of the sudden it's dark. This makes no sense; the amount of light should merely propagate from the light source (sun or whatever else), decreasing in intensity gradually. Because of this, going into water feels entirely wrong. Similarly, if I stand next to a light post in real life in the middle of the night, just because I'm close to a light source, doesn't mean I can see into the dark; it just means I see where the light is.