A real overland vehicle must have a snorkel. Most people will now a snorkel as a breathing tube to keep the water out of your lungs. With a car it's no different. The snorkel gives you a better wading depth and prevents water getting into the engine. But in our case we probably won't be driving through bonnet high water because when that happens our cabinets in the back are most likely ruined.
In our case the snorkel is there mostly for the looks and to keep the dust out! Yes, a snorkel is good for this as well. When driving behind another car on dirt roads most of the dust clouds are quite close to the ground. With the snorkel you raise your air-intake and therefor preventing your airfilter clogging up with dust too quickly.