The swimmers

I had this dream where my mother and I are sitting near a river. There are two men in their late 20s laughing and swimming there. As I am watching them, my mother tells me, "This is a huge, huge river... So vast that it looks like the sea and you can't see the end of it. Many people go on a quest to find the end of the river and many think that they have found it..."
In the meantime, one of the swimmers sees what looks like the end of the river and exclaims to his buddy, "Oh look! There is the end!" Both swim eagerly towards the "end" of the river.
"But when they reach it, " continues my mother's voice, "They see that there are many, many more miles to complete."
At this point, the swimmers reach the "end" only to realise that the river still stretches miles ahead of them. Determined, they continue swimming.
"After a while, you think you have finally come to the end of the river..."
The two men finally come close to a point where they can't see any stretch of the river and start paddling faster.
"But beware! It's not really the river's end... Rather, it is where the river falls..."
The men are just about to reach the final spot when they realise that they are actually swimming toward a waterfall. They are shocked and start panicking.
"And when this happens, it's time to turn back and swim in the opposite direction."
After a lot of effort, the swimmers turn around and swim away, successfully saving themselves from falling down the stream.
My mother looks at me and smiles.