You Are Born Exploding by Rich Larson

You Are Born Exploding by Rich Larson (Clarkesworld #183, December 2021) is set in a near-future world where an artificial asteroid has infected humanity with a xenovirus that causes people to mutate into shamblers (later described by the narrator as “monstrous eldritch crayfish things”). After humans change into shamblers they migrate to the oceans and disappear into the deeps.
All this SFnal content is, however, largely in the background at the beginning of the story, as we can see in the opening scene where Elisabeth the narrator and her son Jack go to the beach. Although biocontainment staff are disposing of a shambler there (“remove him efficiently and with good technicality”, according to the guard), the focus is on Elisabeth’s prickly interaction with a neighbour:

[Jack] points a fat finger down the beach. “Shambla, mumma? Is it? Shambla?”
Alea coos and chirps. “They’re speaking now! Such fun.”
“He’s speaking,” Elisabeth says, bristling. “Jack’s a boy unless he eventually decides otherwise.” She adjusts Jack’s hat. “He’s two now. Yes, Jack, it’s a shambler.”
Alea settles back on her towel, with a curve to her lips that looks more amused than chastened.
[. . .]
A ways down the beach, a small knot of spectators has gathered about ten meters back from a distinctive shape. It’s crawling for the surf, red-and-blue flukes rippling from its bent back. A guard is busy zipping into a hazard suit, white with what looks like a gasoline stain across one knee. The shambler seems to sense its time is limited; it scoots a bit faster now, dragging a wet furrow behind itself. The whole thing is quite macabre.
“Is hubby back from his little trip?” Alea asks.
“What?”
The ejection is more forceful than she intended it. She was distracted by the shambler, and by the sputter and whine of the buzzsaw the guard will use to dismember it.
“Benjamin,” Alea clarifies. “Is he back from Australia?”
“Not yet.” Elisabeth shifts her gaze to Jack, who is meticulously pouring fistfuls of sand onto his tiny knees. “My brother is coming to visit, though. He’s an artist.”
Alea smiles dryly. “Here to freeload while he seeks inspiration, I suppose? Every family has one.”
“He’s quite successful, actually.”
“Oh.” Alea gives a pensive moue. “I think we’re all artists, in our own way.”
Elisabeth imagines gouging out her eyes and filling the holes with sand. “What a lovely thought,” she says.

The rest of the story is a slow burn that is largely a study of the tough but tetchy Elisabeth and her relationship with Jack (who we later learn has a genetic condition) as (spoiler) her personal and the wider world fall to pieces. During this slow disintegration her artist brother Will turns up, and we find he has become interested in the shamblers and has started painting them. Later on, he finds a ledge on a cliff that they use to drop into the ocean but doesn’t report it.
Meanwhile, there is background detail about the rest of the world—the increasing chaos, the haves who get immunomods to stave off infection, and the have-nots who do not. We also learn that some people have started joining anthrocide cults, and are voluntarily infecting themselves with the xenovirus. This division in how people are responding to the crisis becomes obvious when her brother brings a new acquaintance round for a drink (“Will is always fucking meeting people”, thinks Elisabeth):

The air is fresh and electric, and it seems impossible that the world is ending, but that is where the conversation invariably leads.
“You see, this is not like the other plagues and pandemics,” says the ex-sommelier, in a faint Romanian accent. “This is their photo negative. Their chiral opposite.”
“Well, it came by artificial meteor,” Will says, with a buttery smile. “That’s quite unique.”
“It came with purpose,” their guest says. “In my opinion, it’s a gift.”
“How do you figure?” Elisabeth asks, more bluntly than usual.
“In my opinion,” the man repeats, “humanity has been offered a way to save itself.” This prompts her to verify, again, that the front gate’s biofilter reported him clean. “To save itself from itself,” he continues, stroking the small bones of his dog’s head, “and this time, the downtrodden lead the way.”
Will gives an alarmed smile. “That’s quite the idea.”
“First shall be last, last shall be first, et cetera.” Their guest places the dog in his lap. “We left the poor behind, over and over, but now they finally get to leave us behind.”
“By becoming monstrous eldritch crayfish things,” Elisabeth says. “Such luck.”
“By growing iridescent armor and returning to our primeval birthplace,” the ex-sommelier says. “They are safe in the ocean while the old world burns. Or they would be, if we stopped senselessly hunting them down.”

Shortly after this Elisabeth asks the visitor to leave, and later on her brother is ejected too (Jack later falls ill and, when Elisabeth checks the house’s video feeds, she sees that Will has smuggled some shambler carcass into the house to get one of the colours he needs for a painting of one of the creatures).
The final arc of the story sees Jack’s health continue to decline, but this is due to his genetic condition and not the xenovirus. Then, while Elisabeth has a bath, she starts thinking the impossible:

“Wash you knees,” Jack suggests.
He is sitting on the heated tile beside the tub. She can’t deny him, not so close to the end, not when his little limbs might give out at any moment. He’s playing with a bright red fire truck that used to be his favorite. The fact feels disproportionately important now. She feels the need to recall everything about Jack, every habit and preference. He has only been briefly alive, so it shouldn’t be difficult.
“Wash you knees, mumma,” Jack says again.
Elisabeth rubs at her kneecap, feeling the gooseflesh around the bone.
“Wash, wash, wash,” she sings. “Wash, wash, wash.”
“Good washing,” Jack decrees, in an uncanny imitation of the nanny’s synthetic lilt. “Good job.”
“Thank you, Jack. I thought so, too.”
Jack returns to his toy. Elisabeth reaches forward and drains the bath a bit, listening to the gasp and gurgle of exorbitant water waste, then adds a shot of hot water. She stirs with her hand until it’s tepid throughout. Climbs out dripping.
“Jack,” she says. “Do you want to come inna bath, bubba? With your fire truck?”
He is momentarily suspicious, but the novelty wins out. He lets her peel off his clothes, hold him fruitlessly over the toilet, carry him back to the tub. He gives a squealing giggle when she skims his feet through the water, holding him under the armpits. She sets him down carefully and clambers in after him.
“Lots of animals live in the water, Jack,” she says. “Should we play pretend?”

Elisabeth then researches ways of disabling their immunomods. Then she gets back in touch with Will. When she tells him what is happening with Jack, he agrees to help.
The final scene sees her meeting Will at the shambler ledge on the cliff. He gives her the injectors that will disable the immunomods and infect her and Jack with the xenovirus. After Elisabeth and Jack change, they shuffle off the ledge and fall into the sea. There is a great payoff line:

But when they are far from any shore, the smaller hooks itself to the larger. They dive together, toward a city that might exist.

Although this is a quite a slow burn to start with (I had to take a break in the middle as I was beginning to lose focus) it comes to an ending that is both emotional (all those interactions between Elisabeth and Jack come to a moving culmination) and transcendent (the final hint that they will have another kind of life beneath the waves). It is also at this point that you realise that this wonderful story is about Elisabeth and her son as much, if not more, than anything else.
****+ (Very Good to Excellent). 14,150 words. Story link.

1. This story was joint second in the Clarkesworld Readers’ Poll for their 2021 stories. It is the best of them by a country mile.