There not sealed against water intake. Just intended to draw in cleaner air from higher up. A lot of snorkel vehicle owners, including myself, have been disabling them because the sound is so annoying.
I'm wondering if anyone else is noticing this. Whenever I get out of my TH the rock sliders always rub the back of my calves. The back of my legs get wet and/ or muddy from them. They're also worthless to help reach things on the ARB roof rack. I'm having to carry a stool around to be able...