

I use casting plaster from a local hobby store. A little messy, but easy cleanup with water.
I use the gyroid infill and leave a 25mm hole in the bottom. Slightly over-fill then sand flat after it dries.
Adds a pleasant heft and is super easy to use.

Eh. I’ve had good luck with PETG, which won’t break down in contact with water. It helps to print three or four walls, and some simple post processing really seals the deal (ha! sorry for the word play).