The downstream speed is (x/6) km/h and the upstream speed is (x/8) km/h. 。

So the speed of water is: (downstream speed-countercurrent speed)/2 = (x/48) km/h.

So it will take 48 hours at the current rate.

It took 1 hour to go after it when it fell into the water.

During this 1 hour, the lifebuoy flowed to B at the speed of water, while the ship flowed to A at the speed of countercurrent, which lasted for 1 hour.

The total distance between them is:

(x/48+x/8)* 1=(7x/48) km.

It shows that the distance between the ship and the lifebuoy is (7x/48) km when the lifebuoy is found falling into the water.

On the way, the ship dropped the circle and reached B at the speed of water, and the circle reached B at the speed of water. In this way, the distance can be pulled apart every hour:

(x/6-x/48)* 1=(7x/48) km.

Therefore, combined with the previous analysis, it is found that when the lifebuoy falls into the water, the distance between the ship and the ring is (7x/48) km, so it has fallen into the water 1 hour.

Depart at 6 o'clock and arrive at 12 (it takes 6 hours).

So: the circle falls into the water at 1 1