Wario Land 3: Part 69: A Town In Chaos (Blue Chest)

Head to the earliest doorway you can reach at 0:22. When inside, go down to the first doorway you see at 0:43. Its room contains an Electric Propeller Fan, which you must activate in the next room past it, where the Blue Chest is located. With the fan activated, Wario can use its powerful updraft to float upwards, though he doesn't seem to like it much. The Blue Key will be to the left of you in this room, but the only way to reach it is to carefully take an enemy over to the Enemy Blocks protecting it. Wario can't carry enemies while riding the winds, so you'll have to throw an enemy up the platforms and over the wind current. The Blue Chest treasure is a sapling that is then dumped into the ocean for some octopus enemies to eat and grow big. This makes them powerful enough to smash through certain barricades in both The Tidal Coast and Beneath the Waves, creating more routes for Wario to go through.