Footage of a woman pushing a panicked toddler in a swimming pool and watching as she cries was uploaded on TikTok, with the comments disabled.
Shannon, who calls herself a “paediatric drowning prevention specialist”, has previously received messages from “trolls” telling her she is terrifying kids.
But the mum says she is teaching tots to float on their backs so they do not drown if they fall in a pool.
In the clip, which she uploaded on her @whynot0818 TikTok channel on October 14, Shannon pushes a baby wearing a pink coat into the water.
The frightened-looking youngster immediately begins to flail her arms and ends up on her side, with her face half-submerged in the water.
She cries and shouts and slowly manages to float on her back, although her legs keep twisting sideways.
“You clever thing,” Shannon says, before lifting her out of the water.
In the on-screen caption, the instructor wrote: “Crying = breathing.
“We want to find our children face up in the water.”
Although Shannon has fans who say her work is “essential”, other people find it unpleasant viewing.
“Would you like to be thrown off a boat to in the ocean and see how your survival is?” fumed a critic in her previous video.
A second blasted: “That’s not ok you should not just throw a kid into the water and let them be scared like that and it’s not only this kid but the other girl.”
The Centers for Disease Control and Prevention (CDC) says that two children a day die from unintentional drowning.
It recommends installing swimming pool fencing at homes with pools and “formal swimming lessons” to prevent deaths in children aged from one to four years old as well as “close supervision”.
The CDC says that swimming pool fencing of at least 4ft in height can prevent 50% of drowning deaths in tots and swimming lessons alone are not enough.
This comes after a mum received death threats for a video that showed her throwing her baby in a swimming pool.