Do you have wiring to it as well?
Do you anticipate needing to 'unencapsulate' it in future for repairs? If not, simply dunking the wires plus circuit in liquid rubber would give you a waterproof coating and a small amount of mechanical protection. If you want more robust protection you could coat it in epoxy. I think the professional approach would be to place it in an enclosure and fill the enclosure with a potting compound, which is usually epoxy or some form of plastic.