You know how right after you jog or lift weights, you feel fine, but the next day your muscles are tender and sore? This phenomenon was first described by Dr. Theodore Hough in 1902. He called it delayed-onset muscle soreness, or DOMS.

But today, 115 years later, scientists are still debating why it happens.

Well, dangerous and severe discomfort can set in after swimming, too. The conditions are called atypical or dry drowning, and secondary drowning. But we know exactly what causes them.

Atypical drowning happens (mostly in kids) when you take in water while swimming. Such a near-drowning experience triggers laryngospasm — constriction of airway muscles — and that deprives the body of oxygen.

Worse, when you try to breathe, that suction disrupts the junctions between cells in the lungs, triggering edema and making the lack of oxygen even harder to correct.

"That's why every child who's fallen into the water or experienced a near-drowning should be taken to the emergency room immediately," says Dr. Purva Grover, medical director of Cleveland Clinic's Children's Pediatric Emergency Departments.

Secondary drowning occurs when someone (again, usually a child) has gotten water into his or her lungs without being aware of it.

If it causes pulmonary edema, within an hour there's rapid or difficult breathing; however, sometimes symptoms don't show up for 24 hours.

Then they can include respiratory problems plus vomiting, lethargy and a lack of desire to eat or drink.

Seek medical attention immediately if your child experiences any of these symptoms after being in or around water.