Originally Posted by Kos-Mos
I HAVE THE SOLUTION!!!
Get a Mosfet! the fet itself can be made watertigh with a bit of sealing silicone (like in your bathroom, around your bath) The motor can run completely submerged (yes I tried it, in fact I run my new motor in water + alcool for 3 minutes.... help shaping new brushes)
Battery can be made watertight too with the help of the same silicone. everything else, just clean-up a bit after... that is all
You really don't want to immerse a motor in water. The armature plates are a mild steel which rusts up pretty fast. Ferrite magnets also corrode quickly. If you've got an aftermarket motor you'll probably rust up the bearings too. DC motors really aren't meant for water immersion.