No, humans cannot survive underwater without any equipment for extended periods. Unlike marine mammals like whales or dolphins, which have adapted to live underwater and can hold their breath for a considerable amount of time, humans are not equipped to survive underwater without assistance.
The primary reasons why people cannot survive underwater for long periods are:
Lack of Oxygen: Humans rely on oxygen for respiration, and our lungs are not adapted to extract oxygen from water. We need to breathe air to survive, and underwater, we do not have access to the necessary oxygen supply.
Pressure: As you go deeper underwater, the pressure increases significantly. The human body is not designed to withstand such extreme pressure, and as a result, it can cause serious injuries or even death.
If a person were to go underwater without any equipment, they would quickly run out of breath and be unable to survive without resurfacing for air. The exact duration a person can hold their breath underwater varies depending on factors such as their lung capacity, physical fitness, and whether they are trained in techniques like free diving. However, it is typically measured in seconds to minutes, not hours.
As for how deep a human can go before being crushed by pressure, that point varies as well. At around 10 meters (33 feet) deep, the pressure is roughly twice that of the surface, and some physiological effects, such as nitrogen narcosis, can start to occur. At much greater depths, around several hundred meters (over a thousand feet), the pressure becomes lethal, leading to conditions like "the bends" (decompression sickness) if a person ascends too quickly.
To explore deeper depths underwater, humans require specialized equipment like submarines or diving suits that can withstand the pressure and provide life support systems to supply oxygen and regulate temperature. Even with this equipment, there are still significant risks associated with deep-sea exploration, and it requires thorough training and expertise to ensure safety.