A Raised Air Intake (RAI) isn't designed for deep water wading. It's designed to allow the engine to breathe clean dust free air when used in dusty environments. They normally have a water drain hole in the bottom, to allow water out, should it get in. This water drain will allow water in, so the vehicle be driven in water deep enough to submerge the bottom of the RAI.
The D3 has a maximum wading depth of 700mm, with the suspension at off road hight, but LR don't suggest running in water deeper than the height of the upper wheel rim. Going deeper risks water getting into places where its not welcome, like the alternator, timing belt, air intake or the interior.