What an awesome entry. Cave diving sounds fun, and I think the module does a good job of that. There are some parts that doesn't sit with me just right:
- Judging from the screenshot, I assumed you intended for the whole layout to be much bigger, but in the pdf, it's much more small, evidence from the massive margins, leaving alot of white spaces. Alot of typos as well and I can't really select the text on the pdfs, but this is minor stuff that I'm sure can be revised quickly.
- I would've more ways to deal with the river spirit other than just combat. I think the immiscate spell is a nice stuff, but we can go further than that. In the random encounters, there's a section that explains one of the sections falls apart. Seeing this is the mine too, I would love to see explosive solutions to this (miners in Area 4 has mines but has no fuse, PCs can use these mines to explode the blockage.
- I think Wilford can be a more helpful npc instead of just letting him sit there, trading his knowledge. I mean, what relevance is his knowledge for gold is for the PCs, or to destroy the river spirit? Maybe if the river spirit is weak to gold, then Wilford servers a purpose. I just don't see his usefulness, or what is the reward for the PC to venture to his place.
Overall, I can still feel the idea from the theme, and I say it was well done executed. Amazing effort nevertheless. Good work!