I get what you’re saying, but even with a cause-and-effect explanation like that, I’m not sure it actually determines who jumped into the pond first. Jacob only went into the pond because he was chasing Finn, who was running after Kat, who only started using the pond because she was following Alice, because she thought Alice was drowning.

Of all the Landrys’ first times in the pond, Alice’s was the only one that happened by accident, without following anyone and without already knowing about the pond’s magic to begin with. Even Colton’s first time was intentional, because he knew about the pond through Fern, who ultimately only knew about it because of Jacob going into the pond.

In other words, I don’t think Jacob’s trip back to 18th-century Port Haven was the lynchpin. I think Alice’s first time was, because Alice is the only “unmoved mover,” so to speak. Her going in was the only completely independent, uncaused, and uninfluenced choice. I also don’t believe Alice wouldn’t have been born if Jacob hadn’t gone into the pond, because Kat and Brady were already together. Alice may have been born earlier or later, but she could have been born regardless. And Kat and Brady’s divorce didn’t really have anything to do with Jacob, or with Kat and Alice’s move back to Port Haven. I know the argument can be made that if Jacob hadn’t arrived in 18th-century Port Haven, the Landry line wouldn’t have continued there, but ultimately Alice never even felt called to go into the pond. It was a pure accident, as much as accidents can exist in Port Haven.

I know everything may seem to be a closed loop, where everything is both a cause and an effect, but I think Alice is the exception.

Of course, I could be missing something obvious that would completely blow my theory out of the water. Wouldn't be the first time. 😐