I'm currently playing in the Ruins of Azlant AP and as there's a lot of under water combat, I wanted to clarify how this spell would work. Being magical, and not stating that it needs to anchor to anything, I would think that it would "float" in the water and remain exactly where it was cast.
Secondly, when cast outside of water, can you stack two of them on top of each other, thus doubling the height?