I love the dark graphics and hand-drawn aesthetics, very Shadowdark. The town of Undertow, the Cave, and the Fugu-folk have great character. This has awesome vibes!
It took me a little while to figure out how the 2d8 exploration/encounter table works. For enemy encounters, you have provided cool monsters, but does the GM decide which ones, how many, and whether to include those or other Shadowdark creatures every time? The Hazards seem more manageable for a GM to improvise.
I have to agree with folks that "She, Most Deep" is an excellent, ominous name. Good work!