An enclosure for an ultrasonic transducer is configured for variable moisture protection. During storage and transport, the enclosure may be kept in a sealed state, which prevents entry of humidity. During operation in a wet environment (e.g., in a water meter attached to a pipe) water leaks into the enclosure very slowly, even when sealed. Accordingly, a tube is opened, allowing water molecules to be exhausted from the enclosure and absorbed by a desiccant within the water meter. In an example, a tube passes from an interior of the enclosure to an exterior of the enclosure. An end cap on the tube prevents humid air from entering the enclosure during storage and transport of the ultrasonic transducer. During operation in a humid environment, removal of the end cap allows air exchange to ventilate the enclosure and allows a desiccant outside the enclosure to absorb humidity exhausted from the enclosure.