None, I just have normal offshore pumps and outfall pipes, I just used an outfall pipe and a bit of my sea turned into less deep water in the area.
I originally had a offshore pump there which I then replaced with an outfall pipe after that one sucked a bunch but not all of the land was sucked before switching so when I switched them I just noticed that the land in the range of that outfall pipe has become the wrong depth, a shallow depth instead of deep depth. It might have been some issue with the fact that I placed the outfall pipe on a shallower depth than the ocean so it cloned that depth and turned the ocean that