When Lin Fan jumped into the water, there was only a second where he was in the water before there was a force that pulled him under.
This force didn't pull him into the fountain, but rather a hole that was waiting for him.
As he fell into this hole, Lin Fan could feel the fluctuations of spatial laws around him. This confirmed his guess, there was something hidden in the fountain that activated spatial laws to move whoever jumped in.
But he still didn't know where this wormhole would take him.
It was just a good thing that he didn't have to wait long to see where it did take him. It was a very short fall and when Lin Fan came to the bottom of the hole, he fell out in the middle of the air.
However, with Lin Fan's reactions, it didn't take him much to do a flip in the air to negate some of the force of gravity before landing on the ground. But the same couldn't be said about Mo Ze Chen who had fallen into the wormhole before him.