You can get reverse osmosis filters for boats, which turn ocean water into drinkable water, for a few thousand dollars. There's some discussion over whether that's safe to drink long term, since it removes all the disolved minerals that tapwater and well water and ground water have[1], so some people then remineralise it.

Pictures of reverse osmosis filters show a lot of plastic containers with plastic tubing between them.

[1] https://waterfilterguru.com/how-to-remineralize-reverse-osmo...