Abstract: A hydrodynamic seal efficiently protects an interior cavity of an enclosure from external elements. The seal has an upper portion having a recess formed in a center section of the upper portion. A lower portion, having a raised portion, abuts the upper portion and forms a passage between the two portions. The passage between the upper and lower portions is reduced in area along the recessed and raised portions. When air with water and/or dust passes through the passage, a velocity and pressure change occurs, thereby the water and/or dust is deposited in a channel. The water and/or dust flows along the channel and is exhausted to an external so that the water and/or dust is prevented from entering the interior cavity of the enclosure.