what i do is,
i poke a tiny hole in the polythene, and stick the actuator hole tip out of it.
then i apply the glue gun so that the actuator tip is stuck to the polythene making a water tight seal.
then wrap the polythene all around it and stick with the glue gun,
finally seal of the area where the wires are coming out.
dont have the picture of the actuator tip.