You don't use the Mule to get across the lake.
When you first exit Scrap's interior - there's a few dumpsters.
One of them might have something that may... lift your spirits.
Then, when you get to the first area in the actual junk yard, Rooter may want to check out... openings.
And there, he might find a metallic stick to fetch.
Use what lifted you and the metallic stick to cross the acid water.
Fully disclosed, all run together as one large word with a strike through to prevent easy reading in case you don't want it spoiled:InTheDumpsterThereIsAHoverBoardThatIsNotEnoughHoweverYouWillNeedRooterInTheNextScreenToGoIntoTheBackOpenVentsOfTheBuriedPlaneThingHeWillThenDigAroundAndBeAbleToReachTheSilverPoleWhichFallsBelowUseTheHoverBoardAndThePoleToCrossTheLake
Note: When you do the Rooter thing mentioned above, I recommend moving Mule down by the crane - I've found leaving Mule on that first area, causes Rooter's "fetch" to result in an endless mouse cursor spin.
See this for a visual for the Rooter thing:
https://itch.io/post/1990770