Hi!
I like to drive in deep water - like 1- 3 ft. and about half a year ago I extended all my breathers to the air box. If anybody wants to read the write-up it is here -
http://4x4offroadinfo.com/modifications/breathers.htm.
So far seems to work fine, although I haven't checked my diff fluid since then. One time got some water droplets from the airbox to the in-line little filter. Seemed like the filter stopped these droplets from going further. But I don't think it will withstand heavy water flow through the hose.