How a Snorkel Head Prevents Water from entering the engine

I am often asked how a snorkel head can prevent water from entering the engine.

Air and water have different viscosity (thickness) and weight. Because water is heavier than air it will have greater momentum and greater inertia than air. This means that when it travels at a speed, it will take water longer to change direction than air.

When the water and air enters the snorkel head (like when you are driving in the rain), the air will follow the path of less resistance and go down the snorkel intake pipe.

Because water cannot change direction as quickly, it will continue in the original direction and collide with the inside of the snorkel head. The water will now run down the snorkel head plastic .

Because there is a gap between the snorkel head and the snorkel intake pipe, water will flow out of the head via the slots in the head.

Thus it is important that those slots are always open a free of debris.

See sketch below.