The kit protects your footpads and your electronics from splashing water, and doesn't void your warranty if applied correctly (see the FAQ for more details). Submerging your Onewheel is probably still a bad idea.
VERIFY your components are sealed
The Badger Sniffer-Snorter is a pressure/suction device that seals over the vent hole of the controller and battery modules. The vent allows air through but blocks water.
In Sniff mode, the Sniffer-Snorter will create suction as it tries to expand. If it expands, you still have some leaks that need to be fixed. If it doesn't expand, you know your system is sealed.
FIX the leaks
The Badger kit includes two types of electronics-safe, flowable silicone sealant, one thick and one thin, for different types of leak points. The instructions guide your through all the common leak points. Keep going until you can VERIFY your leaks are all sealed. Usually you can get to 100% in a couple tries without removing your battery box (there are MANY places this board can leak, and they are usually all exposed and easy to access). You don’t have to remove your controller but it’s highly recommended and doesn’t void your warranty.
Sometimes you miss a spot. If you’ve sealed all the likely suspects and you still aren’t 100% sealed, you can use Snort mode to find the exact location of the leak.
In Snort mode, the Sniffer-Snorter slightly pressurizes your battery and controller module, so you can find leaks by looking for the bubbles from Windex or other bubble solution you provide. Snort mode is not recommended as the bubble solution can potentially leak into your board. It should only be used as a last resort. After using Snort mode, you need to fully dry the affected areas before attempting to seal them.
PROTECT your footpads.
Water can soak in to your foodpads over time and damage the wood. The edge of the footpad near the wheel is particularly vulnerable, because it gets worn down by dirt and sand being thrown up by the wheel. The Badger kit seals and protects the wheel edge of the footpads with a wear-resistant plastic. It also seals around the bottom to keep water from seeping in.
The Badger kit works with Flight Fenders and non-stock footpads too. You just have to adapt the standard procedure to fit your setup.