Creating a magical grove in a sewer

I’ve been learning Blender for the last 4-6 weeks and my latest project is this magical sewer grove for a player in one of my TTRPG campaigns. I think some of the basics are there, but it’s not yet cohesive. I can experiment for ages but I thought I’d put it to greater minds than mine.

The thrust of what I’m going for is an sewer cistern with a small dirt island, lit by bioluminescent fungi. I’ve included some area lights and glowing crystals to make it a bit more interesting to look at.

I’m a complete compositing novice, but know that can make a world of difference. The fluid sim is also…fine. But I’d have preferred a white water stream from the ceiling into the water below, and am unsure how to achieve that with a single sim. Different materials on each inflow/geometry?

Grateful for any advice you may have!