What's that smell

OK, so yesterday I went down stairs to do laundry and i got doing some things down there and i could smell a disgusting smell. So i got looking around to see if i could see what this smell was, I went in the furnace room, the laundry room, and my treadmill room and i still couldn't find this smell. So i thought for sure it must have been the drain to the washer, so i dumped a little bleach down there thinking that would help the smell. I thought i had cured the problem for sure, but i could still smell it a while later. But then I went into the bathroom down there and oh my heck i about died! There was water everywhere . All over my pictures, scrapbook stuff, swimming things, oh it stunk bad, so I tried cleaning it up, i put towels down, fans on. And it still smells way way bad. The night before the kids were in the tub. (Dad was tending) and they had a whole bunch of water all over the floor. They were just making a "slip and slide" they said and it leaked down there and made a huge stinking mess. I could've just died. So if any of you have a solution to help with the smell I would love to hear them. I tried putting a candle down there, i sprayed odor ban, every spray possible and nothing is helping.