In The Last Jedi, Luke Skywalker went to the ledge, outside of the First Jedi Temple, laid his hands on a large stone, and started meditating. Soon, the water in the pool inside, with the mosaic of the Prime Jedi, began to ripple. What was the cause of this?
A friend of mine suggested it was because of Luke's reconnection to the Force. But what did the water pool have to do with it? Was it some kind of a tool for connecting and disconnecting oneself with the Force?
Another friend thought the water somehow resonated of Rey's entering in the Mirror cave of the Dark Side. It happened roughly the same time in the movie, and maybe the cave was right underneath the pool.
Could someone please explain what made the water in the pool in the Jedi Temple on Ahch-To ripple?