Gearbox and transfer case breathers
The short answer is yes, unless you like water in your gearboxes. Breathers are open to the atmosphere and will allow water in if they are submerged. An alternative would be to put a check valve in the breather that only works when pressurized from the inside. If you do this you run the risk of sucking water in past the seals when the gearbox is cooled by the water. I would just extend the breathers it's easier and cheaper.
Thanks for that. Extending would be the way to go.