Lately, it seems as if everyone and their mother has a "Lifeproof" case for their iPhone. Seriously. If my mom had an iPhone she would absolutely buy one of these.
The logic behind it seems to be that the average life is wet, rough, and crazy (enough said on that subject...) and that one should always use protection. For your phone. C'mon, people.
But how do they work? Typically, they contain a series of seals made of a relatively malleable type of rubber. When compressed and then held in place by clasps or screws, the rubber conforms to the other surfaces, forming a watertight seal.
For those of you looking to waterproof anything homebrew style (you know, waterproof a sink or a cat or a little sister just for fun), the trick is in the type of rubber, the surface it's conforming to, and the way it is held in place. The rubber must be flexible enough to meet up with the surface, but not so flexible as to deform and let water in. The surface has to be flat and straight, something it's easy to seal against. And finally, the rubber must be kept under essentially as much pressure as possible to maintain a seal.
So that's it!! Post pictures of any waterproofed cats/sisters in the comments below!