We give Forti-flora and pumpkin at our rescue as something could be upsetting their stomachs.

Try changing kitteaz diet. If that doesn't work take the little furry to the vet! If you have the money take kitty to the vet ASAP!

Cats are notorious for acting very normal even if they are sick so even if the diarrhea is the only obvious symptom, there could be more going on. The obvious question is if there were any changes to his food or anything he may have gotten into. Lots of cats, including one of mine, has a fussy stomach and gets diarrhea with some foods.

I don't worry if it has been only a few days. Will your vet process a stool sample without making an appointment to examine Munchie? Would be the cheapest way to start if they do.

You can check for dehydration by pinching his scruff - if it takes longer than normal to return to pre-pinch state he's dehydrated and should be seen by the Vet (for fluids).
I'd give it a few days and see if it resolves on it's own - drinking the mucky water might have been the trigger.

Go to your local pet store and see if they can make any suggestions that would less expensive then the vet since you're currently out of work..

If it is more than a few days... call the vet. To save time you might ask if bringing in a stool sample (turn siploc bagt inside out and get some from litter box), might help save diagnosis time.

Couple of days yep could be bacterial enteritis

If its been more than a couple days, I'd call the vet

if it persists and there is a change in his behavior, for sure take him to the vet. One of my kids has a cat with kidney problems and frequently had the shits. Now she is on prescription cat food... Luckily her mommy makes a bigger salary than her grammy does, that stuff ain't cheap.

When in doubt ALWAYS have your Furbaby checked...Wish I could do more.