Dreadstar,
Very sorry to hear you lost your receiver! A simple way to prevent this from ever happening again, besides correcting the leaky hatch, is to buy a few party balloons.
The put your new receiver inside the balloon, with the wires and antenna sticking out of the top of the balloon, then use a wire tie to seal the neck of the balloon.
Not sure if balloons have necks, but you get the idea. I 'd do the same to my battery pack.
When the boat is not in use I take the receiver out of the balloon to prevent any condensation from forming. I like yellow balloons myself, don't think the color will effect anything, if you don't like yellow.
There are a number of ways to properly seal your hatch. The foam you use is important. Open cell foam leaks. I use a high density foam with adhesive on one side as my gasket and then added a couple of servo arms fastened to the deck on the sides of the hatch to put additional and even pressure on the hatch. If you need any more info I can send you a picture or two that show this approach. Tape works but is a real pain and looks terrible. Not to mention trying to get it off.
Good luck
Windchaser