Mantec Snorkel and Wading Kit
The Land Rover we hired for our 2007 southern African trip did not have a snorkel. Although we were slightly miffed by this (all expedition vehicles must have a snorkel to show that they are driven by serious offroaders!), we soon got over our disappointment. Until that is, water came over our bonnet while crossing what looked like a shallow stream in a game reserve in Botswana.
For some reason the close proximity of hippos and crocodiles made Lisa reluctant to follow the guidance to wade any water obstacle first to see how deep it is.
Fortunately, we surfaced without any engine or other damage but then spent several hours trying to find a way back which did not require retracing our route.
This experience reinforced the wisdom of wading first to test the depth of any water hazard and the desirability of having a snorkel other than just for aesthetic reasons.
The other (primary?) benefit of a snorkel is that it gets the point at which air for the engine is collected up and out of the dust thrown up by your own wheels and (if you are travelling in a convoy or on a busy road), the vehicles in front of you. My experience in Morocco was that despite travelling in convoy on some very dusty pistes was that the air filter kept remarkably clean.
Foleys fitted a steel Mantec snorkel and plumbed in extensions to the axle breathers.