The events loop over and over
The events of the movie Triangle loop over and over. Each time they are repeated, new copies of the main actors appear. The actors from the future sometimes encounter the ones coming from the past just like what happened with Jess when she saw her past versions.
Future Jess encounters her past versions
After all the group is killed, except Jess, the loop is repeated again and the whole group arrives once again to the ship only to find another copy of Jess existing, which is the future Jess. In this case, future Jess finds herself face to face with past versions of her friends.
Jess realized she must kill the group
As the loops kept getting repeated over and over, Jess realized that she has to kill everyone in the group for the loop to start again. This is why future Jess is equipped with a gun and is more hostile than the past Jess who has little idea of what’s happening.
Future Jess wants to prevent the group from boarding the ship
Future Jess, or the experienced Jess, concluded that if she prevented the group from boarding the ship, the cycle will stop and the infinite loop will end. This is why future Jess decided to keep repeating the loop until she manages to prevent the group from reaching the ship. (See Ouija: Origin of Evil (2016) Movie Explained)
Past Jess finds items left by future Jess
The reason the original Jess found her keys in the beginning of the movie is that future Jess dropped it. The same goes for many of the items such as the kill-them-all note, the necklace and the jacket. Whatever future Jess left can be found by the past versions of Jess.
Jess couldn’t end the loop properly
The reason Jess found another copy of herself when she returned home is that she didn’t end the loop properly. Instead of killing all the members of the group, she was pushed into the sea by one of her past versions and so the loop wasn’t stopped. (See The Number 23 (2007) Movie Explained)
Why the loop keeps getting repeated
The loop keeps getting repeated because whenever future Jess gains enough knowledge on how to stop the loop, one of her past versions manages to push her into the sea and so the loop repeats itself.
Jess boarded the ship to re-start the loop
In the end of the movie, Jess chose to board the sailing ship again in order to start the loop once again and try to prevent the bad events from happening.
Jess might have killed her son
According to many fan theories, Jess might have killed her son in the very beginning of the movie as a result of failing to control her temper. She then went to the boat trip with her friends after she committed her crime.
Jess refused to accept her son’s death
In the end of the movie, the mysterious taxi driver told Jess that he can set her free if she accepted what happened and returned to him. Jess refused to accept what happened, and as a result, she boarded the boat and so triggered the start of the loop.
The loop could have began in the harbor
This infinite loop could have began in the harbor when Jess refused to accept what happened to her son.