This is some concept work from when I was Environment Lead for Shape of Water at MrX VFX. A talented team of lighters, FX, assets and comp had to build parts of it based on some of these images. There was much thought put into the symbolism and underlying reference to what the water felt like. It was not meant to feel like clear, pristine open ocean but more mysterious, murky and brackish.
This shot was cut but it was one from inside the creatures tank. GDT called it the 2001 shot. It was after the creature was injured and captured. Red was symbolically meant to be Eliza's color while seafoam green was Strickland and more royal blue's was the Creature's. I think if were to do this again I would use real volumetric renders to help get the lighting more balanced.
First image below was the original footage we worked with. Roto was the real hero here! We then had to try and re-imagine the volume and lighting. These were all experiments before the final blue-version was picked.
I used reference from brackish water scenes/freshwater lakes to make it feel more like Baltimore (the film's setting) or perhaps the creature's original environment (Amazon). Here is one my research sheets that helped inform the asset artists:
