Ultimate RC discovered in their review of the Fury that despite the labeling, the AS-1 servo is NOT waterproof. I don't know if the ADX-7M servo in your BLX is just labeled waterproof or if it actually is. If you don't know for sure beyond the label that you have a "proper" waterproof servo, then I suggest avoiding puddles all together. Assuming the servo is waterproof, then you need to ensure that the Rx box is sealed correctly. Sometimes in an RTR it's not assembled as carefully as we might ourselves. So I for one would double check that the seal is correctly in place all around the Rx box. Depending on how hard core you're going to get with the water I might even run a very thin bead of silicon along the seal of the Rx box, and where the wires enter/exit it. As far as the motor goes, if it get splashed it's going to just need a wipe down. If it gets submerged, it should be thoroughly cleaned out and the bearings lubed with a light weight oil. I use 3-in-1 myself.