The word "strand" serves as a lynchpin of the whole game, with several different meanings used that all play an important part in the devastated world.
The most obvious association is whale stranding, with Sam having to face several whale-like BTs over the course of the game.
In various Germanic languages, "Strand" means "beach", with the Beach being the equivalent of the afterlife for characters.
"Being stranded" means "being lost without any obvious solution to move from somewhere". A lot of characters are stranded on the Beach and in the world of the living, unable to move on.
"Strand" also means "thread", and that meaning of a thin strip is why it means "beach" in some languages. BTs have strands connected to them that allow them to exist in the world of the living.
The cufflinks characters associated with Bridges wear also a pun on the idea, with handcuffs having two important parts: the part with the teeth that latches on is called "single strand", and the part with the locking mechanism is called "double strand".
The rope Sam carries is called a "strand", it has his blood woven into it, which helps to identify him to the scanners in knot cities and prepper shelters. A DNA strand, if you will.
The game features a lot of references to pregnancy and childbirth, and its connection to being reborn.
For starters, the most obvious one is the fact that Sam carries BB around in a fake womb.
Sam is tasked with the delivery of packages, which help people in rebuilding their settlements, in a way helping them be reborn themselves. He also ends up "delivering" Lou, both in the sense of bringing her out of her womb and into this world and in the sense of saving her from exploitation and "decomission" at the hands of the Bridges corporation.
After death, Sam wakes up in a sea and has to guide himself back to his body. He wakes up nude and underwater, like a fetus in an amniotic sac.
The ringtone NPCs use to call Sam sounds an awful lot like the first verse of "Rockabye Baby on the Treetop", a common lullaby. Heartman's codec ringtone, on the other hand, sounds more like Chopin's Funeral March.
Speaking of ringtones, Die-Hardman's ringtone sounds like the first part of "London Bridge is Falling Down."
Death Stranding seems to be an antithesis to certain themes previously covered in the Metal Gear series.
Obviously, the differences between Snake and Sam. Whereas Snake is a soldier, Sam is an Action Survivor deliveryman. Snake can afford to use lethal force against hostiles, and people who played as him didn't have to deal with the resulting corpses aside of hiding them. But Sam is actively discouraged from killing humans. Sure, he can, but doing so can have dire consequences—consequences that Death Stranding actively confronts the players with, as killing creates BTs and leaves behind corpses that have to be burned properly at incinerators. Otherwise, the player will soon find their gameplay loop further hampered.
Instead of complete stealth, Sam is encouraged to leave his tracks behind, as enough players using his route will eventually create a natural footpath—one that can mark a safer route through dangerous territory.
Lockne wanted a child who would carry her genes. The child was given birth in a manner that would have made that implausible, if not impossible: as a Beached Thing.
Snake is injected with nanomachines that make him much tougher than a regular human. Sam on the other hand is physically delicate, even gripping his hand will bruise his skin. He also needs regular rest and his stamina has to be managed either by sleeping or drinking energy drinks. The nanomachines speed up Snake's aging process, and his fear of and acceptance of getting old and dying are a central part of Metal Gear Solid 4: Guns of the Patriots. Sam on the other hand can't die for any reason other than old age, despite multiple suicide attempts.
Solid Snake is snarky, cocky and sure of himself. Sam is awkward, submissive and not very talkative.
While Snake isn't devoid of empathy and feelings, he rarely shows them, prefering to act. Sam's empathy is what allows him to gain allies and ultimately avoid the end of the world. He's frequently crying and often shows fear, pain or outright panic.
Sam's reaction to first setting both cuff links to his wrist seems more appropriate for being touched, given his aphenphosmphobia. The cuff links work by being physically connected to its user, so to Sam, it more than likely feels like someone gripping his wrist.
One Impossible Task a prepper gives you is to fetch some gear from the destroyed ruin of a Knot City that was nuked and is now full of BTs. Radiation is not considered an issue...because of the Timefall there! The half-life got sped up so much by the Timefall that the nuclear particles there decayed to safe levels quickly.
With only a few exceptions, all traces of the pre-Stranding civilization of the USA are gone: not even old roads or skyscrapers remain in the landscape. The shells of buildings you do find are explicitly those built by the Bridges I expedition, and those look ancient now, despite the fact that they were made within the last three years (i.e. the expedition's lifetime). This is because the Timefall has eroded everything away completely, leaving it looking like humans were never here at all. A great excuse for the game world to look completely empty before you work on rebuilding it.
Equipment degradation is usually something rather...amplified for a game's effect, but in a world with Timefall it's made much more explicit why your high-grade military gear turns to junk. (Notably it only decays when you're exposed to the timefall, so a clever player can avoid a lot of hassle if they stick to clear areas and make use of timefall shelters). A brilliant case of Gameplay and Story Integration.
Many people speculated after the first trailer that Sam might be ex-military due to the Q-pid looking like dog tags. As it turns out, the Q-pid is what allows settlements to joint the chiral network, in turn joining the UCA. As it turns out, Sam was never a soldier to begin with. But he is related to someone who was: Cliff, one of the antagonists, and Sam's father. It's openly said by him that he was only good at dividing people (makes sense, as a soldier separates people simply by killing them), while Sam brings them together. The item associated with Cliff is his dog tags, a symbol of his military service and his metaphorical nature as a divider; while Sam's is the Q-pid, which looks very similar, but actively serves an opposite purpose.
Biblical equivalents: Sam comes up against a trio of antagonists that somewhat loosely bring to mind "the Father, the Son, and the Holy Spirit".
Cliff as "the Father". Specifically, he is Sam's father, his ghost brought back and manipulated by Bridget/Amelie. (Naturally before drawing this conclusion, Bridges largely assumes that Cliff was under Higgs' influence. Speaking of whom...)
Higgs as "the Son". This seems like the weakest equivalent, as despite some of their early similarities (e.g. the "go" finger gesture from Trailers 2 and 3), he and Cliff are not connected at all; but Higgs serves the Final Extinction Entity, and comes into direct conflict with Sam, whose connections to Cliff and Amelie make him a "rival Son" of sorts to Higgs, The Antichrist.
Bridget/Amelie as "the Holy Spirit". She is the final Extinction Entity, and while people have seen her via hologram, none of those people have met her or come in physical contact with her. Powerful and untouchable—words that can as easily describe God or Amelie.
Bridget/Amelie wears outfits of three different colors. Bridget wears white, while Amelie wears either red or blue. Red, white and blue—the same three colors that make up the American flag.
Anybody who has delved deep into analyzing P.T. has undoubtedly found this use of color in that game's final puzzle/set of loops: the flashlight changing between red, blue, green, and yellow at random. Colors that match up with the logos of both PlayStation (Sony) and Microsoft. Judging by the new Kojima Productions' partnership with Sony and the platform DS was first released on, it was probably the former.
After his death in the prologue, Sam wakes up on the Beach to find a crying infant beside him. He cradles the infant, trying not to completely break down himself...but he stops when the infant suddenly disappears from his hands. In Episode 14: "Lou", Sam opens the pod to free the dying Lou, and tries to resuscitate her. When he thinks the child has died, he cradles the infant in the same way, fighting back tears...but is suddenly snapped out of it by Lou coming to and babbling.
The scene of the dying Bridget falling out of her bed and crawling toward a terrified Sam was bad enough with the ubume parallels (a bloodied abdomen), but it becomes even more chilling with a skull mask covering her face, making her crawl toward Sam more intimidating.
Sam's first and last long-distance deliveries to the incinerator as a Bridges porter, not as a freelancer. The first time, Sam is tasked with President Bridget Strand's cremation, but is not told about the other cargo that he was meant to burn: BB-28. Sam's final delivery is explicitly for BB-28/"Lou" itself, after Deadman takes Sam's cuff link offline. In both occasions, Sam saves Lou from being burned. The first time, he carries out his order to cremate Bridget, thereby "burning his bridge with her", but hesitates when told to do the same with BB-28; the second time takes it further by not only saving Lou from being burned, but by Sam leaving his cuff links to burn in her place—thereby "burning his bridges with Bridges".
The cutscene following Sam's final battle against Cliff in the Vietnam War-themed Beach, and Cliff's final moments with Sam during the memory of their original deaths.
Sam finds Cliff leaning against a fallen tree, and chooses to approach him. When the memory has John aim at Cliff—who's now leaning against his wife's hospital bed—Sam immediately gets between them. Both times, Sam physically lowers himself to Cliff's eye level, of his own volition.
Cliff is more lucid than he was previously, but he still seems to think that Sam's BB Lou is his BB. It's not until Sam asks "Are you Clifford Unger?" that he becomes more lucid, able to ask Sam who he is. The memory of Cliff's death carries this onward; he's at his most aware here, halting the memory so that he can talk to Sam.
"They told me your name is Sam Porter... But you're Sam Bridges. My bridge to the future." This line seems out of nowhere, especially from a soul who had previously attacked Sam three times out of instinct already. In true Kojima fashion, it's revealed to be a metaphor for Cliff's connection to Sam: Cliff as the father, Sam as his son (or "bridge").
After saying that, Cliff stands up on his own, with his dog tags in hand, and has Sam stand up. In the memory, Cliff gets up by using Sam as a handrail—or a bridge—and has him stand up, waiting to give his son the BB in his hands.
After receiving the tags, Sam hesitantly hands BB-28 to Cliff; after a moment, Cliff hands the BB back to Sam, because it's not his child. In the memory, Cliff has no such hesitation, giving the BB in his hands to Sam. Sam asks if this is his infant self, but Cliff doesn't answer.
Cliff then embraces Sam, his military fatigues replaced with his suit, then a moment later—BANG! And with that gunshot, Cliff disappears. The memory sees Cliff giving his tags to Sam again, cupping the collar of his suit as if getting a good look at his son's face, them embraces him one last time. Then a gunshot breaks the moment, and the memory resumes, with Cliff and the infant Sam now dead.
It's fitting that the afterlife looks like a beach, since all life as we know it originated from the sea. So inversely, the souls of the dead (as seen in Heartman's flashback), would naturally be drawn back into the sea, thus passing into the Seam.
A flashback shows that Amelie's Quipu necklace was a present from Sam; when Sam told her it could be used to count things, Amelie told him that she'd add another knot every time she saw him. At the end of the game, when Sam successfully resuscitates Lou, she is holding Amelie's necklace. Since Amelie severed both her Beach and herself from the mortal world, and will never see Sam again, she didn't need the necklace anymore.
Your reward (as of update 1.08) for linking up the First Prepper to the Chiral Network is... a Santa hat. At first, this seems like a simple holiday easter egg as the hat itself does absolutely nothing... until you consider who Sam is: a man who treks across wide stretches of land, braving harsh elements to bring people what they need, and is said to perform Impossible Tasks on a regular basis, fostering hope wherever he goes. Who else is known for performing seemingly impossible feats of delivery and is widely seen as a symbol of hope? That's right, Santa Claus is the original Great Deliverer!
Three generations of women who are close to Sam have very similar names: his biological mother and Cliff's wife is named Lisa, his wife was named Lucy, and the BB he took out of the pod and is essentially raising as his own daughter is named Louise.
The animals in the Seam seem to be alive and well, but still swim belly-up, which is commonly seen in dead water animals like fish. This is because the Seam is a place between the world of the living and the dead, so it's natural that the creatures inhabiting it would be suspended between the two states.
Of course "J" from the Cyberpunk 2077 crossover missions is Jackie Wells rather than Johnny Silverhand. Depending on player choices, when the game's event happens, and whether one considers Johnny's engram to be Johnny's soul or not, Johnny either passed away fully into the afterlife (the original Johnny in the backstory and the engram in most endings), is locked in one person's mind as a kind of Beach (Johnny during the events of the game), or has fully returned to life (in the Temperance ending). By contrast, if Arasaka manages to get their hands on his body, Jackie ends up as a malfunctioning engram missing vast swaths of his mind.
BBs are harvested from their brain-dead carrier (Stillmother) at 28th week of pregnancy. It's impossible that this is done with the parent's consent. What about the child's second parent, or the carrier's family? Are they notified of their family member's brain death and the fact that their child is going to be put in a pod and carried across the dangerous terrain by a complete stranger, who may or may not treat them well? In one of the emails, we find out that some porters cause autotoxemia in their BBs on purpose. As far as we know there's no consequences for this.
Borders on Fridge Squick. After Sam repatriates, he vomits up some chiralium and cryptobiotes. The catch is that the cryptobiotes are alive and run away the second he pukes them up. Does this mean Sam or Fragile can feel them wriggling and moving in their stomachs? A more optimistic take is that the cryptobiotes can be found in the waters of the Seam, so it might be that Sam swallows some water (and cryptobiotes) during repatriation by accident, so the ones he throws up have been in his stomach for only a few minutes.
Even weirder possibility: when Sam repatriates, the dead cryptobiotes inside his stomach repatriate with him simultaneously.
The sky is always cloudy or hazy and you never see the sun directly. It's possible given the nature of the setting that the reason is something even weirder than this, but consider all the voidout craters dotting the landscape. All those explosions must have kicked enough dust into the air to dim the sun, like the aftermath of a nuclear war.
Throughout the game, despite being a helpful and encouraging boss, Die-Hardman seems somewhat shady and untrustworthy, even for a man in a skull mask. It's only when you watch the final cutscenes that you realise he's been keeping an emotional distance from Sam out of guilt for killing his father, Cliff. This also explains Deadman's mistrust - he's been somehow sensing the underlying tone of Die-Hardman's relationship to Sam.
Animals do not have beaches. Yet the Death Stranding was responsible for multiple mass extinctions in earth's past. But once you consider how the time fall erases most traces of human civilization, pretty much nothing being left of old earth and even only years old structures looking like they have weathered centuries, it has some horrifying implications. Humanity in Death Stranding most likely isn't the first sapient species, nor in all likelihood the first advanced civilization. Just another in a row to get ravaged by this event.
