This was a really fun game, that made my truly question my understanding of boats (and the concept of weight!)
Had a couple of naggles: although the game recommends fullscreen, it caused the coins to be extremely small on my 4K monitor. Changing my res to 1080P resolved this but possibly some scaling would be appreciated!
The core mechanics were very fun! And the length of the game didn't mean they didn't get to boring. My only gripe was at the end of the game: my boat hovered at about -2.5M when it reached the surface (it was quite big so some couches were in/out the water!) It then took about 10 minutes of adding balloons before my boat raised from -2.5M to 0M, which felt like a bit of a massive waste of time.
Other than that it was very well executed - Never heard of LibGDX before! Will have to check it out!