How to unlock the Waterproof achievement?

I'm playing the game Forager (version 1.0.3) on Steam.
One of the Steam-achievements of this game is called Waterproof, supposedly earned by covering every water tile.

So far, I've covered all(?) water tiles with landfill, buildings or bridges but didn't yet unlock that juicy cheevo.

The Internet offers conflicting information which most likely stems from earlier versions of the game. I. e. one guide said I could place landfills beneath bridges (not true), another mentions I could have to place a land fill block last, due a bug (tried with no success).

Which of these count as "covering" water tiles?

• Buildings (light houses, oil platforms)
• Bridges
• Dungeons with visible water spots underneath (the ice dungeon seems to be placed on water, do I need to move that somehow?)

Or did I do everything correct already and just missed a spot somewhere?

Solution 1:

I managed to get the achievement after all.

• Two spots below the rainbow can't be filled
• Bridges count as filled
• Oil platforms count as filled
• Water tiles below dungeons/towers count as filled
• Fish traps count as filled
• the lighthouse counts as filled