I have a relative with a phone by his pool

He uses an old rotary phone for it, because it's all pretty basic electromechanical stuff that can't really get messed up from it being out in the rain or whatever. It can't make outgoing calls because modern phone systems don't work with rotary phones, but it receives incoming calls just fine

It should maybe be noted that he's an old school telephone lineman who really knows his stuff, so I don't know if there were any other adapters or anything needed to make his setup work.