> If there's a bit of water in your lungs,
a surprisingly small amount, it causes massive inflammation and
your lungs start to fill with fluid. It's called
"secondary drowning", and it happens a couple of hours after.
Allow me to quote an article from Cleveland Clinic Journal of Medicine https://www.ccjm.org/content/85/7/529 (AI generated nonsense of course)
> Secondary drowning, sometimes called delayed drowning, is another term that is not medically accepted. The historical use of this term reflects the reality that some patients may worsen due to pulmonary edema after aspirating small amounts of water.
> Drowning starts with aspiration, and few or only mild symptoms may be present as soon as the person is removed from the water. Either the small amount of water in the lungs is absorbed and causes no complications or, rarely, the patient’s condition becomes progressively worse over the next few hours as the alveoli become inflamed and the alveolar-capillary membrane is disrupted. But people do not unexpectedly die of drowning days or weeks later with no preceding symptoms. The lungs and heart do not “fill up with water,” and water does not need to be pumped out of the lungs.
> There has never been a case published in the medical literature of a patient who underwent clinical evaluation, was initially without symptoms, and later deteriorated and died more than 8 hours after the incident. People who have drowned and have minimal symptoms get better (usually) or worse (rarely) within 4 to 8 hours. In a study of more than 41,000 lifeguard rescues, only 0.5% of symptomatic patients died.
Maybe don't set too much store by what some random "water rescue course" instructor tells you, especially if it sounds like complete bovine excrement.