Thank you for your answers. My question was probably not clear enough.

Even if the cylinder is not filled to an excessive level with water, water can "bubble up" when it is bubbling and then enter the main shaft, i.e. the thing that encloses the gas cylinder, via the arm. It then gurgles and splashes in there.

I get a little bit of water out by shaking and swivelling, it then flows out at the connection between the shaft and the foot.

The stem is open at the bottom, you screw the carbonated bottle in at the bottom. I've never had anything leak out of it.

The first thing to say is that no/hardly any water collects in the collecting basin (I assume you mean the "shaft"). The carbonator does not let any water out, only air.
If some water does get into the small basin, you can simply remove the cover and either remove the moisture with a cloth or tip it out in the sink. The Carbonator is fairly light and can be emptied easily.
But as I said, this problem does not arise in everyday life (at least for me).