Originally Posted by A Useless Geek
All you Polaris guys should be keeping the upper fuselage compartment water tight by mounting the ESC with the heat sink sticking up through the upper skin. The ESC can be held in place with RTV or something that will keep the water out. That way you don't need any holes to bring in cooling air.
Like most scratch builds or kit assemblies it is the builders choice. Polaris requires a hatch to change batteries, an option is another hatch to access ESC/receiver/servos, etc. I chose to make my ESC's water resistant through the use of Liquid Tape with my first Polaris and Corrosion X with the second and the XL, which has the ESC mounted with heat sink through the upper skin.
To date I have dunked all three, and had seam leaks and depron cracks on the first Polaris. All three receivers and ESCs have gotten wet...no malfunctions after drying for a couple of days.