Yes they can be placed on any surface that underground pipes can connect through (so in SA, everything but lava and empty space)
By "pumps" do you mean the things used to speed up fluid flow or pumpjacks used to pump oil?
I mean the ones that speed up fluid flow. The Cargo Ships mod adds offshore oil that can be mined using oil platforms and allows pumps to be placed on water. However, the platforms only have 1 output per edge, which limits the loading of tanker ships to 1,200/s in all cases. I would like to add more pumps on one side (like train fluid loading with 3 parallel pumps), but that isn't possible, since pipes can't be placed on water.
I tested your mod and underground pipes can't connect to pumps unfortunately. I can think of two "fixes":
- allow underground pipes to connect to pumps directly (kinda cheaty)
- allow the pipe-to-ground to be placed on water (makes more sense logically and visually)