There's no rule against overlapping or intersecting areas of effect
Zones can overlap, and the rules for both apply. Generally the same spell can't affect you twice, so overlapping two castings of the same spell is a bit pointless, but with two casters throwing out spell effects that create zones on the board, there's no general rule that would prevent it from working.
That said, visibility can be a definite concern. In the case you mentioned, the hunger of Hadar zone is magically dark, so you can't target a point inside it with another spell that requires you to see the point you're aiming at. That said, as long as your target point is outside the hunger zone, the area the spell creates can extend into the darkness -- you are not required to see the entire spell area (unless the spell specifically says you are).
Wall of water says, "You create a wall of water on the ground at a point you can see within range. You can make the wall up to 30 feet long, 10 feet high, and 1 foot thick." (A ring shape is also available.) Like wall of fire, it doesn't say how the wall is shaped or where the 'point' is with relation to the wall, so I'll refer you to a few previous questions that discuss those two issues with regard to wall of fire:
What are the permitted shapes of a wall of fire?
Casting wall of fire in a T-shaped corridor
The second one there is really the important one in this case. Note that there is a slight difference in that wall of fire doesn't require you to see the target point. However, based on those answers, presumably the wall of water is a straight line, and the point of origin just needs to be somewhere along the line, but there's enough ambiguity there that your DM could certainly decide to rule otherwise.