Sometimes when you ask if a game is coming to Linux it's a no, others say it's planned and when it's Buoyancy the developer just puts up a build soon after asking.

Yep, that's what happened here. After asking about Linux support on Steam, developer replied to say "yes". When asking if they knew when, they went ahead and uploaded a build. If only it was always that easy…

If you've not seen it before, here's their most recent trailer:

It certainly seems quite unique. A city-builder where your city travels around, one you need to defend against pirates and avoid nasty weather. There's no Beta to opt into, you just buy it and let the developer know how it runs in this linked Steam forum topic.

You can find Buoyancy on Steam where it's currently rated "Very Positive" from users. Some of the reviews make it actually sound genuinely good too.