Volvo Penta dpsm bellows question

[hard knox]

Any experienced Volvo techs out there that would like to explain how the drive shaft bellows stops water from getting to u joint ? I have been a automotive tech for over 30 years and cannot see how there's any way do to design it can stop water from reaching u joint. Please explain if you can. Thanks 

[lost a lure]

The u joint is inside the bellows sealed at both ends

 

[hard knox]

On the drive unit we're bellow should seal there's 4 notched out sections for the outdrives input shaft bearing bolts . That in my opinion would cause a leak and looks like a poor design to me .