I like the drone textures, and that is a solid foundation to build on. To take this further, I'd suggest adding some bass or strings to fill out the low end, using automation so the instruments don't cut off abruptly, and dropping in some SFX to fill the empty spaces. Reverb or modulating effects would also help push the sounds past their fundamental tones and bring them closer to an ambient, lake-like feel.
Overall, I get a spoopy—like a haunted fable about a lake vibe, so that's very fun!