Has a hinged Perspex cover. It is located by a pavement on the highway

You missed point it may be below sea level but not under water.but are divers waterproof to 422 metres........
Given my experience of IP44 lamps/fittings filling with water, I'd disagree with that statementSo likely the enclosure shown is IP54 which means Dust protected (with or without vacuum applied to the product) and Protected against splashing water. And in the main that is OK for some thing outside.
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