Question: In the film *[Triangle](http://en.wikipedia.org/wiki/Triangle_%282009_British_film%29)*, we learn at the very end of the film,

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>  that the Jess we meet in the beginning already went through the loop (maybe even all of them). She remembers what happens on the liner, and she must remember that her main goal was to stop the entire crew from stepping onto the liner.
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When the moment comes when the crew wants to be "rescued" by the liner, why didn't she try to stop them? She hesitates, but doesn't act on it. Why?

Answer: 
After watching it again (I felt a lot like Jess, herself) I realised that she does not forget the events that took place until she is back on the Triangle. We can see her very sombre in the beginning of the film (when we have no explanation for it).

The reason she voluntarily goes back is because of what The Driver says about Tommy: "No point trying to safe the boy, nothing anybody could do's gonna bring him back." If you look very closely, you can see the slightest hint of her expression changing, because she has a new idea. It's not her goal anymore to safe herself, she wants to go through hell again (figuratively speaking) in order to prevent Tommy from dying in the next iteration.

However, when she steps on the Triangle, she falls asleep and forgets the previous events (until it's far too late, when she begins to very vaguely remember), as if they were dreams. After she wakes up we see her brightened up significantly. This is when her new plan to actually *get* on the ocean liner is forgotten and everything starts anew.
I got that the final cicle starts at the end of the film, not that it repeats the first one.
The jess of the ending is the jess that wears the mask and gets shot, takes it off to pretend to be the earlier version, lead the couple to the cabin an slits his throat and say's "sorry, but I need to see my son"
She is the cold 
blooded killer, the one with practice. She also says, when referring to the older version Jess that she "is not who they think"
We never see what happens to that one, and she isn't explained in the loop shown in the movie. (Although the woman she stabs in the stomach is, she dies several times on the deck, this is the only part I can't figure out)

(Edit: There's an explanation for all of them. The blooded killer is the original Jess at the end of her story arc. It's her second time boarding the cruise ship and she gets killed by another Jess that has boarded twice and is watched by a Jess that has only boarded once. The Jess's that have only boarded once are the ones that push each other into the sea while wearing the mask. There are basically seven stages to her cycle.)

Stage 1: Jess goes onto the cruise ship and pushes the masked killer (Stage 3 Jess from a previous boat) into the sea. 

Stage 2: Jess watches another Jess in stage 5 kill the unmasked killer that's in stage 7 while comforting the dying Sally. This Jess in stage 5 is the one she points the gun at in the banquet hall. She boarded the ship on the second boat.

Stage 3: Jess becomes the masked killer and gets pushed into the sea by a new stage 1 Jess that was on the third boat to arrive in the movie.

Stage 4: Jess goes home to save Tommy and gets in an accident and decides to go sailing again.

Stage 5: Jess boards the ship with her full memory which is the fourth boat to arrive in the movie. Stage 2 Jess from the third boat points a gun at her and she kills Stage 7 Jess from the second boat.

Stage 6. Jess hides and let's a new Stage 1 Jess from a fifth boat push Stage 3 Jess from the third boat into the sea.

Stage 7. Jess becomes the unmasked killer and is killed by Stage 5 Jess from the sixth boat to arrive.