We have been playing the hobby for several years and have always struggled with the ships once they sank. Not that any of the electronics would be lost; it just took time to dry everything out which usually eliminated the ship from further competing that day. Even water tight boxes are only marginally successful.
We have a lot to learn from the Fast-Gun groups around the country, who have perfected the sink. Ships are able to go down and after recovery, get right back into the next sortie a half hour later. So how do they do it? Well most of the answer is found in two bottles shown here. They are MJ Chemicals Acrylic Conformal Coating and MJ Chemicals Connector Coating.
The conformal coating is used to coat all your servo and receiver electric boards. Just be sure not to coat the male end of the servo plug on the receiver board. You should usually put about three coats on. Once this is done, the receiver can even be left open in the ship, getting wet continually and will not run into any problems.
For coating the servos, you will either need to get waterproof versions or open them up and coat the insides. I have seen where some servos had a hole drilled in the side and the conformal coating applied through the hole. For this you will want to use the spray version which is also available from MJ chemicals.
The connector coating is for… the connectors. This helps prevent water getting into the connector and causing a short or grounding.
For many of the battery connections, you should switch over to XT-Connectors. They come in many sizes, but the most use are the XT-30 and XT-60. The XT-90 would be for your heaviest gauge wiring. These connectors are shown below.
Very few Fast-Gun ships actually had water tight boxes. Most just had the coated electronics loose in the bottom of the ship. I observed 12 battles over two days and there was more than a dozen sinks Without exception, each and every single ship returned to be in the next battle.
So if you want to stop worrying about being sunk, a little preparation can eliminate your concerns. You will also be able to sink and be back in the next battle.
As a last note, after two days of battling, all ships were put up on a table and hosed out. At first I could not believe it; what were they thinking. The pond used copper sulfate to control weeds and hosing the ships out helped get the contaminates out of the ships as much as possible to prevent future corroding.