Buy yourself some CORROSION X .
Then take your servos and RX apart . ( remove covers )
Then take the CORROSION X and soak the insides for about a minute ( this way , everything inside gets coated )
Then , take and pour the remaining ( that is left inside your servos/receiver ) and pour it BACK into the original container .
Then let hang UPSIDE down overnight to dry .
Reassemble your servos and RX and put back into your boat . Wha-la ... water-prrofed !
here is a link to a good deal on some right now :
Greatest stuff for water action RC since the invention of the radio gear !