Alternate Timeline: The first time the first Jess meets the second Jess ignoring the Killer Jess before a new timeline has been created where the other passengers died differently. Subverted in that the two timelines play off at the same time and each influence each other. For example the new timeline eventually causes the second Jess to have her own story, which we don't see, where she eventually killed some of the passengers as the second masked killer which eventually made the first Jess turn into the first masked killer.
Ambiguously Gay: Greg seems to be viewed this way by Downey: "You are living on a boat with an 18-year-old boy and you are asking me not to bring girls." He later also enquires if Greg and Victor sunbathe together. He seems to be implying that the two are involved.
Amicable Exes: Greg and Sally used to date in high school, and still refer to each other as their "ex". They remain best friends to their late 20s when they die.
Amnesia Loop: Both versions of Jess who turn up at the harbor have underwent traumatic experiences and it is evident in their behavior. Later in the timeline of the first of them, she falls asleep for a couple of hours. When she wakes up, one of the first thing she mentions is "I don't remember". During the loop she seems to re-learn things that she had forgotten about. One interpretation is that the loop gives her temporary amnesia and she keeps attempting to recover her memories. When she succeeds, its time for the cycle to re-start.
Anti-Villain: Jess kills all her friends, but she did it in order to stop the time loop from happening.
Apologetic Attacker: "Mean Jess" from the second loop, after she's finished repeatedly stabbing Downey. "I'm sorry, but I love my son."
Arc Number: Several scenes occur in either the residence of Jess or a cabin of the Aeolus. Both are numbered "237".
Asshole Victim: Arguably Sally, due to her bitchy and disdainful attitude towards Jess (even going so far as to snottily refer to Jess' son as a "retard").
Ax-Crazy / Broken Bird: "Mean" Jess from the second loop. We don't get to see her full story, but Word of God believes her to be a Jess who has gone through the loop so many times she's become callous and psychotic.
Bat Deduction / Insane Troll Logic: When she becomes aware from the time loop, Jess tries to prevent the deaths of her companions. Trying to rescue them from somewhat more experienced versions of herself, and consequently trying to stir events to a different reaction. When that fails, she concludes that she has to kill them to end the loop. Because all the previous versions of herself eventually tried to do so. That she has not seen even one of them succeed in breaking the loop, and that she has personally taken out one of them evidently fail to convince her that this method doesn't work either.
California Doubling: Well, Australia Doubling, at least. It is set in America, but was filmed in various locations throughout Australia.
Cassandra Truth: Greg doesn't believe Jess when she claims that she's sure she's been on the boat before, trying to tell her that it's all in her head.
Victor figures early on that something is off with Jess, because she had trouble answering where her son was and then claimed he was at school. On a Saturday. He warns Greg, who ignores the warning and theorizes that special needs schools are open at weekends. Jess is lying and her son is dead by this point.
The cab driver warns Jess that there is no point in trying to save the boy (her son). Yet she voluntarily re-enters the loop in an effort to do just that, despite the mounting evidence that it is futile. One view of the events of the film is that the only way to actually end the loop is for Jess to finally quit trying.
Dark and Troubled Past: Victor. Per the backstory, got in trouble at home (wherever that is), run away, and spend time as a vagrant. Greg found him sleeping at the harbor and took him in.
Designated Love Interest: Greg to Jess. Per his words, he only visited the diner out of hunger and not loneliness. He didn't feel the need for female companionship, until one day prior to the events of the film when he suddenly decided to ask her out. The two are barely acquaintances, and it isn't clear if there is more to their "romance" other than they didn't have anything better to do for the weekend.
Disappeared Dad: Jess raises her son Tommy as a single mother. No indication what happened to the father, though she casually mentions that he was an asshole.
Dreaming of Things to Come: While on board Greg's yacht, Jess dreams of her body washing up ashore on a beach. This happens much later on the film. Due to the nature of the time loop, this scene may instead be a fading memory of a previous cycle of the loop
Fake American: All of the main actors (and a few of the ones playing minor parts) are Australian.
Also the ship itself. According to it's life preservers, it is registered in Miami, but it is clearly modeled after the British pre-war steamer RMS Queen Elizabeth, and even betrays its origins by using the Commonwealthian spelling of "Armoury" instead of the American "Armory".
Fate Worse Than Death: Jess is stuck in a presumably endless time loop (or purgatory, depending on your interpretation) in which she murders her friends and accidentally kills her son over and over again.
First Name Basis: The main characters address each other by first name only: Downey, Greg, Heather, Jess, Sally, and Victor. No family name is ever given. Curiously, they are not that familiar with each other.
Greg is a longtime friend of Downey and Sally, and the current employer of Victor. Jess seems to be a recent acquaintance, and he has never met Heather before.
Victor was an 18-year-old vagrant which Greg took in as an employee and roommate. There is no real indication that he is particularly familiar with the rest of the crew.
Downey and Sally are friends with Greg and Heather. They don't know or care much for either Jess or Victor.
Heather is a friend of Sally, and an acquaintance to Downey. She doesn't know any of the others.
Jess became acquainted with Greg at her workplace, but this seems to be the first time they spend any time together. She has no known previous interaction with Victor, and does not actually know any of the others.
Foreshadowing: Greg points out to Jess: "But you can't be everywhere all of the times". For most of the film, there are multiple versions of Jess running around. Three or more versions, with different timelines, are at various areas of Aeolus at any point in time.
Future Me Scares Me: Jess threw the masked killer overboard which she later finds out is herself. The second time it happens the killer has even been unmasked, but the new Jess tries to kill her anyways.
"Groundhog Day" Loop: Jess witnesses the death of her co-passengers from different views because apparently the whole situation starts all over again when they die. Subverted because for everyone she has killed apparently the corpses stay.
Except sometimes they survive for a bit longer, only to die in other ways, in other places, and sometimes their bodies stay... or don't.
Hollywood Autism: Tommy, son of Jess, is a mild example. Male child who is unable to live what most people would call a normal life. Otherwise his behavior is not that abnormal for a child, including an interest in painting, a tendency to leave his toys everywhere in the house, and leaving the occasional accidental mess when handling liquids.
I Hate Past Me: Future Killer Jess, having gotten tossed off the boat, finds herself at the beginning of the day and sees herself physically abusing and yelling at her kid. Hating what she used to be, and having long since jumped off the slippery slope she smashes her past self's head in and tries to take her place. Somehow this does not result in erasing herself from time, but sets up an infinite loop.
I Thought It Meant: It's not a film about The Bermuda Triangle, despite what the title and part of the premise may lead some to believe. However, Word of God states that one of the early ideas was for it to be a Bermuda Triangle film, and, although that idea was scrapped, some of the mythology surrounding the Triangle did make its way into the plot.
Its location in Miami and the waters outside it, seems however to place it within the Triangle. The Triangle as originally defined in 1964, is the area between the cities of Miami and San Juan, and the island of Bermuda.
Ironic Hell: Everything mean Jess has tried to do to get back to her son (killing her friends being one of them) has led to her being directly responsible for his death, starting the sequence all over again.
Made of Plasticine: In the midst of trying to convince Victor that they keep dying and coming back to start everything all over again, Jess accidentally kills him by pushing him into one of the pointed hangers attached to the wall, completely penetrating the back of his head.
Subverted a bit in that he doesn't die right away, and in fact appears to suffer a bit of brain damage and die from an internal hemorrhage rather than the wound itself. Still, a hanger piercing that deep into the skull is not likely.
Actually this seems quite legit as the hanger seems to penetrate the part where the skull and spine connect, there is a small area that isn't protected neither by the skull or the spine, you should be able to even feel it when your neck muscles are relaxed. However this raises the other question of how does he keep moving around after having his spinal cord snapped.
Mama Bear: To save her son Jess is willing to kill her best friend and everyone else on the yacht. And when she comes across a third Jess mistreating him she murders her.
The Matchmaker: Sally is not too subtly trying to be this for her single friends Greg and Heather. Greg is rather frustrated with the idea, and points out later that Sally keeps trying to bring him an eligible girl "every year".
Meaningful Name: The name of the ship, Aeolus, refers to a mythological Greek figure whose son, Sisyphus, was doomed by the gods to roll a boulder uphill for all eternity, where each time he reaches the summit the rock rolls over him and then back down again.
Mind Screw: You're gonna need multiple viewings to actually get everything, and even then you'll either be confused, thinking there's gonna be a sequel or that a sequel is impossible.
Narnia Time: Subverted. Jess ends up back home where her son is still painting, but she's actually still stuck in the time loop.
Never the Selves Shall Meet: Averted. Jess throws the masked killer overboard, threatens the second Jess which created a second timeline, gets motivated by the second Jess who turned into the second masked killer to become the first masked killer and gets thrown overboard by the third Jess which will apparently walk the exact same path she did.
Jess discovered a grate in one of the ship's rooms through which she could see a whole pile of the locket she wears which indicates that there are presumably several if not many other Jesses that went through the loop, but she never meets them. Then her locket falls in with the rest...
Once More with Clarity: The opening scene shows several brief snippets of Jess' morning. We see this scene again toward the end of the film, and it becomes clear that the parts that were skipped over were Jess verbally and physically abusing her son.
Perpetual Frowner: Jess. She very, very rarely smiles, and when she does, it seems to be forced rather than a genuine smile.
Many of the loop's elements have no logical beginning, in a sort of My Own Grandpa situation.
Reset Button: Killing the other passengers is a reset button. Only it isn't a reset button.
Rule of Symbolism: The "Mean Jess" (as she was nicknamed by the director) from the second loop (the killer who was a lot more callous and brutal than the other Jesses) has a bullet skim the top of her head, causing blood to run down it. Later, the "past" version of Jess who is seen abusing her son has blood running down her face in the exact same pattern, from the exact same spot.
Shout-Out: According to the commentary, the killer wearing a sack as a mask is a Shout-Out to Friday the 13th Part 2, in which Jason Voorhees wears a pillow case over his head prior to the iconic hockey mask.
As seen several times through the film, there is a message written in blood on the mirror of room 237. This is a direct reference to The Shining, where there is also a message written in blood on the mirror of room 237.
There is a seagull which constantly follows Jess around, and which she is revealed to have killed in a traffic accident prior to the sailing trip. Per the director, this is an allusion to The Rime Of The Ancient Mariner. The seagull is a stand-in for the albatross which the mariner killed, the event which set off his curse.
Another allusion to the tale of Ancient Mariner is the weather pattern of the sailing trip of the Triangle. Following the death of the albatross, the fair breeze blows and all seems right. Until they realize that the breeze led them to uncharted waters ,and then that breeze fades to dead calm. Trapping the ship of the Mariner.
The Mariner and his companions also met a ghost ship in the poem. A ship with only a deathly-pale woman and Death as its only passengers. Notice how pale Jess looks for much of the film. As for the description of the woman in the poem: "And is that Woman all her [ghost ship's] crew?/Is that a DEATH? and are there two?/Is DEATH that woman's mate?/Her lips were red, her looks were free,/Her locks were yellow as gold:/Her skin was as white as leprosy,/The Night-Mare LIFE-IN-DEATH was she,/Who thicks man's blood with cold."
The music in the record that Jess listens to is a rendition of Anchors Aweigh by Glenn Miller and his band. Miller famously disappeared while flying over the English Channel in 1944, and the music is probably an allusion to the fact that Jess and her companions are not about to return.
The original Sisyphus, who Jess seems to imitate, is said in the film to have cheated death, though the characters fail to remember how. While there are several versions of his myth, there is one where he broke a promise to the death gods. His family failed to offer him proper funeral rights, and he convinced the death gods to offer him a second lease at life in order to prepare his own funeral. He promised to voluntarily return to the Underworld and then failed to do so. In Triangle, there is a sign which says Goodbye, Please Return and Jess later promises the cab driver (a ferryman like Charon?) that she will come back to him and pay for her ride. Which she doesn't actually intend to do.
Slashed Throat: Downey, in the second time loop. This doesn't kill him straight away, and he ends up being stabbed repeatedly by Jess. He lives long enough to attempt to scrawl the name of his killer in his own blood, but dies partway through.
Stable Time Loop: Jess comes to the harbor looking dazed and eventually ended up being on the mysterious boat and threw a masked killer overboard. She realizes the "Groundhog Day" Loop and tries to break the chain by killing herself becoming the masked killer and getting thrown overboard. She drifted back to the shore where she was able to hitchhike back home seeing herself with her son. She killed her other self and wanted to dispose of the body which resulted in a car accident killing her son. She gets on a taxi to go to the harbor and the trauma seems to have caused amnesia. She comes to the harbor looking dazed and eventually ended up being on the mysterious boat, etc. etc. etc.
The trauma didn't cause amnesia. Jess gets on the boat at the end with the intent of killing everyone to reset the loop, then going back to fix things surrounding the incident with her son. The Jess that gets on the boat at the end is the Jess that is involved in the first loop which we don't get to see all of (when she was wearing the black jacket and went ape shit on the guy in the cabin). The time split didn't happen when she killed herself on the boat, it happened when she killed herself in the house.
Word of God states that one of the possible interpretations of the film is that amnesia was involved... starting when Jess wakes up from her nightmare looking bewildered, almost as if she doesn't know why she's there.
Unwitting Instigator of Doom: At one point Greg mentions that he decided to invite Jess to the sailing trip on an impulse. The previously smiling Jess stares at him and then adopts a sullen expression. One view of this scene is that she just realized that Greg and his impulse unwittingly set off the events leading to the time loop and all the carnage involved.
We Hardly Knew Ye: Due to the time loop, viewers meet several versions of each main character except Heather, who is lost at sea before the main events begin. She is only there for the introductory scenes.
Weather Dissonance: The sailing trip goes well until the weather becomes odd. The ship goes from a speed of 7 knots (8,061 miles /12,98 kilometers per hour) to 0 in mere seconds. A change which Greg, the only experienced sailor among them, quickly marks as strangely abrupt. Then some kind of strange electrical storm turns up on the horizon, heading their way. A quick communication with the coast guard establishes that there is no other report of any strange weather in the area.
What Happened to the Mouse: What happened to Heather after their ship capsized? Other than the surviving suspecting she survived, got on the cruise, and dropped her keys (which was done by Jess by the way), we never know whether she survived, died, or became part of the time anomaly.