Why do you get water infections?

Dont know exactly which ones your talking about so I will touch on a few. If your talking about ear infections that's because when water enters the ear drum and does not dry out, it is a perfect place for bacteria to form, then we get ear aches and the like. If your talking about in a already existing wound then that's because there are all sorts of stuff floating around in the water that enter the wound and get infected. There is also bacteria in ponds, rivers, lakes any water that does not move consistantly including pools and spas, that are not treated properly, either by polluters or not the right chemicals that bacteria grow in and enter the body through either a wound or any orafice on the body, ears, mouth, eyes and private areas. The ocean has the best of all world so to speak, it moves constantly and the salt content in the water does not allow bacteria to form on its own. Not to say that fish cant form bacteria, Im talking about the water itself.