There is a hovercraft (hover board) in the attic of the old mill. If you release the loft gear lock and turn the windmill arms counterclockwise (by climbing on them), you can enter through the roof dome. The hovercraft runs on manure, which is free at the nearby field.
You can cross the mud swamp on Astro Knights Island by using the Hover Boots. These boots will allow you to move across the mud without sinking. You can find the Hover Boots in the Factory area of the island.
The mill is out of commission. The only way to get across the mud swamp is the hovercraft in the mill's attic.
There is no helicopter. There is a hover board in the attic of the mill that will get you across the mud swamp. (see related question)
You have to push it open.
u just press on it
This means you have already completed the Arturus part of Astro Knights Island. Your spaceship should be parked on top of the castle if you return to the planet.
go to the mud with that ting like a hower board over the mud and you will find it in the mud
It goes to the mud swamp, which is the only place that you can use it.
yu dont yu get manure and use it tu get accross
The saucer Excalibur is crashed in the mud swamp to the right of the Mill.
In the underground lab of Mordred, there is a mud wall blocking your path. Push hard and it will fall down.
There is no such power. You can fly on the hovercraft into the mud swamp, and in space aboard the Astro Zone ships. (see related questions)