One of those hints is very important. (Now may be a good time to run thru a Top Ten list of Iowa's largest cities.)
So first off I figured out this happens if I drain water.
That color scheme, I prefer it so much more to the normal one. Not sure if you're interested in changing it but yeah it's cool. Also chiming in on the flashing rave screens, I don't have epilepsy but that is terribly annoying. It's a neat idea but I generally run through those screens as quickly as possible.
Not sure if you mean look there again or for another lake. Everything else just looks like a river to me (besides the four screens mid left) but I'll scan over it again. I do run into a few trees/corn fields that seem like secrets but just appear to be dead ends maybe I'm missing something there. So is this geographically accurate to actual Iowa all the rivers/water I mean?
Unfortunately I'll have to see those dudes again to get the exact hints unless I just need to know Waterloo. I see that it's sort of NE on an Iowa map but nothing seems to particularly stand out. I'll just have to keep checking for secrets.
Welp still have to figure this stuff out but in the meantime I went ahead and finished the game. That boss is uhh...not what I expected.
Umm also I walked up in the final room and immediately teleported through the table to the dudes side. Didn't have to kill fire or anything. Not sure if that was intended.