A few weeks ago I decided to buy a waterflosser, it was on sale at woot so I figured why not. Everything is about what I expected, but there's a pretty serious design flaw, the charging port is at the front base of the flosser and it's wide open. Why is this a problem? Because water can and will get into it, and per numerous reviews I've seen on Amazon this will result in the port corroding and diminish the current it can carry. This will result in progressively lower battery power per charge.
So what's the solution? Some people have reported success in cleaning the port out regularly. Others have replaced the port entirely. I even saw one review where someone soldered on a new power connector to the flosser's board. These all seem like the wrong approach in that they're reactive. Instead why not prevent the problem instead of bandaging the damage? The problem is that the port is open and exposed to water. We can't move the port location on the device, but we can cover it.
To make a port cover I decided to go with a radians moldable earplug kit, I've used them before so I know they're pretty versatile. All you need to do is take a bit of the colored and white putty, mix them, and stick them in the port (make sure to jam it in there so you've got a decent seal). It takes ~10-15 minutes to set. After that you can pull your newly formed cover off. (You may need to cut off excess material with a knife to get the cover to fit snuggly.)
After you're all done you should have something that looks like this. Hopefully this will prevent water exposure.