If a manufacturer of projector enclosures claims to produce WATERPROOF enclosures, then one needs to be very concerned. A waterproof enclosure is actually an impossible product to produce.
Environmental enclosures need air to flow through in order to work with the sophisticated cooling system. If the unit is airtight then projector will soon fail.
Projector enclosures are designed to take air in and allow it to flow out. The enclosure is proven to be weatherproof by undergoing a series of tests which comprehensively check for water ingress. Hence the enclosures are tested by having water sprayed at them from all angles. A clever design allows air to flow, and water to be unable to enter.
This is a serious part of the design process. Ensure that the manufacturer is able to provide documentation to prove that their unit has been tested.