As for me i think humans cannot naturally breathe underwater without equipment. Unlike fish, which have gills to extract oxygen from water, humans rely on lungs that require air containing oxygen. When submerged, the lungs cannot absorb oxygen from water, and attempting to breathe it in can lead to drowning, as water fills the lungs instead of air. The human body can only hold its breath for a limited time, usually between 30 seconds and a few minutes, depending on training and lung capacity. Some people, like free divers, can extend this time with special techniques, but they still cannot breathe underwater.
To survive underwater for extended periods, humans need equipment like scuba tanks, which supply compressed air, or rebreathers, which recycle exhaled air. Without these tools, oxygen deprivation quickly affects the brain, leading to unconsciousness and potentially death. Interestingly, scientists are researching ways to deliver oxygen directly to the bloodstream through liquid breathing or other technologies, but these methods remain experimental and are not practical for everyday use. In summary, humans are not physiologically equipped to extract oxygen from water, making breathing underwater without equipment impossible and extremely dangerous.