A quantity of water that would be enough to make it to the engine would be detectable at the fuel sumps almost immediately after refueling. Now I have already found water droplets in the sump weeks after they were introduced into the system, but those were hardly enough to cause any major issues.
About 40 years ago, I tanked up my 150 at a local airport. I sampled the fuel...and found it full of tiny bubbles. The bubbles didn't go up, they didn't go down. Showed it to the usual crowd hanging in the office. My CFI said, "Hey, it couldn't be water, it would collect at the bottom and besides, there's a water detector on the pump."
Shrugged it off as a curiosity, mounted up, started the engine, and took off. About five minutes later, the engine started to skip. I instantly thought of the bubbles, and firewalled the throttle to get as much altitude as I could. As I got near my home field, the engine was really running rough. Finally quit as I was on final...a HIGH final. Wasn't taking chances. Got it down and rolled up to the airport office. Pulled out my fuel sampler. 100% dirty, filthy water. Ran inside, got on the phone, and warned the airport I'd gotten the gas from.
Then it was drain the water....dump the water. Drain more water...dump more water. Eventually got a larger bottle. I estimated there was at least two gallons of water in each of my 13-gallon wing tanks.
The fill points for the underground fuel tanks at my departure airport were recessed into the ramp. The fill points had filled with water. A bad gasket on the fuel had cap let the water into the tank. My guess is that the pump mixed the water with the fuel to the point where the engine could still run normally...but five-ten minutes of vibration from the engine running had caused the water the separate and strangle the poor O-200.
So, yes, it *is* possible that the water may still be suspension for a while after it got introduced into the tanks.
Fortunately, it was early in the say, and I was the first one to fly in, tank up, and fly out again. The airplane before me was a Bonanza, fortunately based at the field. They drained more than five gallons from him.....
In case this story sounds familiar...I wrote it up, back in the '80s, and Flying magazine published it as a "I Learned About Flying From That" article. My first writing sale!
Ron Wanttaja