In the old days, before Traxis made a waterproof servo. We coated the servo with tool dip, sometime with plastic tape and tool dip on top and an "O" ring under the servo wheel. These lasted several sinks but eventually failed There are even more available water-resistant coatings if you insist on making your own but the Traxis last for several sinks and are commonly used by many combatants. About the only thing that is not electronic board (coated in various sealing methods) is the rudder servo, so not a big deal when it eventually fails several years down the road.
