I’ve recently noticed water in my colony, and I found that this water basin was leaking slowly. [Edit: The white tiles were built after the fact to stop the leakage. Before that the water was just contained by the natural tiles you see.]
I don’t think the game explains this at all, so I’m asking here: Which materials allow water to pass through them, and which don’t?
Typically solid materials don't allow liquids to pass through them. When this happens it's because the tile is getting damaged and will eventually break; the wiki explains how it happens, but to keep it short, it depends on the liquid and the solid.
That basin doesn't look specially big, so if you want to stop the leakages, you probably could do it by surrounding it with normal tiles, usually they're more resistant than natural tiles. Diagonal building helps wonders in this situation (so the water doesn't flow out of the basin while you're strengthening it).
Thank you!