Pretty sure this is a mod conflict, but I can't see anything in Space Exploation that would be causing this.

Any type of Waterfill places landfill instead of water. All Noxys Waterfill is structured like this:

Waterfill: Base mod>Alien Biomes>Space Exploration>Noxys Waterfill>Space Exploration>Space Exploration Postprocess(Required)

Kinda got myself stuck with this. Used Cargo Ships to find myself a nice island, the plan being to fill in the water with Shallow Waterfill (Combined with Noxys Swimming) to make it less cheesy for the Biters. Unfortunatley my Cargo Ship ran out of fuel just off the coast and I don't have enough materials to make a boat to get more materials.

I'll just use AAI vehicles to keep gathering ores on the mainland while I wait for a fix, awful lonely out here though D:

Well this is most likely space exploration doing it so I can't really fix this. The following is also in their changelog:

---------------------------------------------------------------------------------------------------
Version: 0.3.13
Date: 01. 06. 2020
  Bugfixes:
    - Re-enabled waterfill (requires space-exploration >= 0.3.71).

This is now fixed in Space Exploration:

Version: 0.3.74
Date: 08. 06. 2020
  Bugfixes:
    - Fixed a crash with lifesupport gui when on an unknown surface.
    - Issue with Nauvis having climate tags on some saves that prevents waterfill.