Frightening moment during the women's 200-meter individual medley qualifying heats at the 2024 Olympics ... when Slovakian swimmer Tamara Potocka collapsed poolside after suffering an asthma attack.
The 21-year-old first-time Olympian required immediate medical attention after finishing seventh in the third heat at Paris La Défense Arena on Friday ... with staffers putting her on a stretcher with a neck brace and oxygen mask.
Potocka is now being constantly monitored for the next several hours after receiving oxygen and meds, a team rep said in a statement.
"Tamara has asthma," Team Slovakia's Ivana Lange said. "This whole combination of nervous and physical tension while she did not have her inhaler immediately available to use contributed to the creation of this problem."
The medical emergency ultimately delayed the next heat of the event ... before the competition eventually resumed.
The announcers calling the event detailed the atmosphere during Potocka's medical scare ... saying the entire arena went silent, and it appeared to be "very serious."
Potocka -- who has since been confirmed to be conscious and communicating with medical professionals -- missed the cut for the finals ... finishing with a time of 2:14.20.