There appears to be some confusion about the label of “Marine” devices. Marine devices are made specifically, as the name suggests, for use on ships, oil platforms and other industrial environments. They are specially designed to resist shock and vibrations in their moving buildings.
If they needed to be waterproof it wouldn’t be a very good ship!
Applications where wash downs or very damp environments require either linear heat cable or aspiration. Point detectors are not waterproof.