Fixed - same underlying cause as #54 (the flying-ship paddles), which is why the top of the boat stayed put while the bottom slid.

The boat is built from several map-art pieces, and at least one is drawn mirrored. v83 mirrors a piece about its origin point, but our graphics library mirrors it in place, so a mirrored piece with an off-centre origin lands in the wrong spot. When that piece is ALSO animated and its frames are different widths, the wrong-offset changes every frame - which is exactly the 'bottom going forwards and backwards while the top stays still' you saw.

Mirrored pieces are now anchored on their origin and re-corrected per animation frame. Fixed for all flipped map objects, not just the boat.

On the editor preview now; reaches the public build with the next publish.