Adam, you need a wading kit because: axle cases when they hit cold water will create a vacuum, sucking in water, mud and all sorts of stuff. gear box and transfer box will do the same, the vent pipe is there to allow expanded hotair to go out and air to return when cooled.
the bellhousing and timing belt cover will need to be protected, this is better done will a romovable (wading ) plug, put it in when playing and take it out when you finish. this will allow oil and dust to drain out and also the water that will inevitably get in these area's.
If you want a kit that will do all this, with as many vent points as you need, PM me and I will sort you a high quality kit ata good price,
Dave
( Axledeep)