Dirt bikes regularly get submerged under water (while running) and survive after being dragged to shore, turned upside down to drain out the water, change the oil and go. That's not quite the same as being submerged for most of day, but in some ways (the bike is running) is worse.
I had her up and running in about an hour, though this was a two stroke mind you. Road the remainder of weekend Moab trip with no issue. Later when I drained the gear box oil it looked like a milk shake. I’m still running on the same wheel bearings. It sat in water about 5 to 10 min before we got it out.
In your case I would have pushed to have the bike totaled but it I had the opportunity to buy back cheap I would. Ride and get it good and warm, change the oil a few more times and ride piss out of it.