That was a common question I asked myself whenever I'd back up. I had $20.00 auto parts store lights that worked great for a while, but after a some wheeling trips and submersion in water and mud, they stopped being so bright.
Even after repeated cleaning of the reflector and changing bulbs, they didn't quite cut it. Even worse with the top up and the tinted windows installed....
But now, I can see a bit better.
These are sealed and good for submersion for up to 30 minutes, though I really don't want to find out the hard way. The cool part is that they spliced right into my existing harness.