That's not an idea for Koodo, this forum is for things related to Koodo and as such ideas that Koodo can implement. Also the companies that make phones are not the same companies that make cases for phones.
Anyways the closest thing to a waterproof case would be the Otterbox Defender case which protects against water like rain and splashes but there is no fully waterproof cases. You can get a bag type protector to put your phone in that will make it waterproof but it's not a case that you'd want on all the time.
What about the Otterbox Armour, Kid ? Also, this is a Koodo suggestion if he wants to see them at the Koodo kiosks. From what I heard, their selection is somewhat limited with good reason if you think about all the cell phones case stores out there (Pacific Mall in Markham by exemple, there must be like 200 of those in there), it's hard to compete. But I am sure a few Otterbox at the kiosks handy would not hurt.
Not sure if you heard but Liquipel is opening Kiosks in Canada! The first one is being launched at West Edmonton Mall although I'm not sure if there will be other Kiosks in Canada. You should Google it, or watch some Youtube vids because it is some pretty neat stuff.