I have many waterplanes but only one at the moment on 2.4 GHz
On some models, like the jet here, I don't bother wrapping the Receivers in anything special.
I did get water in the fuselage once but the main Rx was well clear and the extra one (mounted under the ply plate with its aerials for and aft) was OK also.

On my other models I often do not attempt to waterproof the Rx. I just mount it on a shelf in the middle of the fuselage and try to keep water out. I have done my Northstars and Lochstar like that.

On others I enclose the Rx in a clear plastic bag, quite loosely. Just to keep water splashes off it directly. You can usually see if water gets in. I always remove it after every flying session to let the air in and dry off any moisture.

If you enclose the Rx tightly, as in a balloon, you can't see if water gets in. You can't get the water out. Water WILL get in nomatter how thorough you are, but it can't get out. You tend to just leave it in the "waterproof" wrapping between flying sessions. Believe me, if water did get in to the compartment in the model, then there will be moisture in the Rx. Even if it's just a little condensation. If water didn't get into the compartment, you wasted your time wrapping the Rx (and you still have to unwrap it carefully just to check it is dry).