When tooling around near cold, polluted or otherwise nasty water, the need becomes apparent for some sort of expensive watertight clothing. Fortunately for the poor/cheap, foul-water protection requires nothing more than roadside trash and American Ingenuity*.
Ghetto waders essentially consist of a garbage bag over each foot held up by rubber band garters - either one per foot or several layers, depending on conditions. In practice, though, some modifications are needed. Since garbage bags are approximately square, and legs are not, a lot of excess material ends up flapping around, which can be wrapped around the leg and secured with another rubber band. The most important problem, though, is the bags' durability - they don't usually rip on the legs, because water isn't sharp and abrasive. But the rocks/sand/twigs/broken glass beneath your feet are. Natch, a junk pair of sneakers slipped over the waders will keep them intact - but, with no water resistance, they will be filled with crap and perma-ruined for any other application.
Ghetto waders don't take up much space in the car/suitcase/backpack - trash bags and rubber bands are useful things to have around anyway - if one pair gets mucked up, making another takes less than a minute and costs less than a dollar.
After your watery adventures end, throwing the waders away is probably the best option due to a) mold and mildew if they aren't completely dried and b) they cost like fifty cents. But if for some reason they need to be stored, you can turn the bags inside out, put the wet shoes in them, and tie them shut with the rubber bands.
* it still works if you're British/Australian though