A multitude of reasons but essentially down to water ingress into various components!

* Oil seals
* Breathers
* Electrics
* Air intake
* Boyancy!!
* Carpets

So, if you want to go through anything deeper than 500mm, you do so at your own risk as it takes more than just a Raised Air Intake (Note: It is a Raised Air Intake.... Not a Snorkel!).

M