Object flips 90 degrees when I add a box Collider - strange

Adding water to my game. Trying to do damage to the player or mobs when they go under water. Thought of a few ways but ultimately decided to use OnTriggerEnter(). My water works fine before, slowly moves up using transform.Translate (its rising water). But as soon as I add a box collider, the water flips 90% at run time instantly, and becomes no longer visible. In the inspector it appears nothing has changed, but in the runtime in the game, the water is no longer visible there at all.

Any ideas on what could possibly cause this? Literally the only thing I have changed is enabling the box collider.

Edit: After further inspection it is actually just rotating my water 90 degrees - what in the.. There is literally zero code that could rotate it. Why in the world would adding a collider cause my water to rotate 90 degrees at runtime?!

Pics:

Before:

After: (At runtime)