The famous paranormal researcher Ivan Sanderson described in his book a case that happened in 1932 in the province of Ibibio. Residents of those swampy places refused to pay the tax, as a result of which a police officer was sent to the intractable taxpayers, accompanied by a sergeant.
However, when the authorities came to the main village, they found it deserted. But after a long search, the guards still found the fugitives who were sitting under one of the steep shores of the island … under water. At a depth of 2.5 meters. Residents tied themselves to the roots of trees with vines and seemed to be sleeping, but the sergeant still managed to "wake up" the people. Then they went ashore and calmly went about their business. By the way, they paid the tax.
It is known that female divers in Japan, ama, are able to dive without special equipment under water to a depth of 25-20 meters, and according to some reports, they can stay there for up to half an hour. Fish women were described in Chinese chronicles as early as the 3rd century BC, and archaeologists continue to find human bones on the islands, deformed due to frequent diving. But, despite the fact that people are able to stay under water for a long time, this does not explain the mysterious underwater "sleepy state" of the inhabitants of Ibibio, who could have been under water for more than a day.
Since the temperature of mammals drops somewhat in the state of sleep, the amount of energy they require is somewhat less than in the state of vigor. Nevertheless, the body temperature of a person in a state of "water suspended animation" cannot equal the temperature of water, and therefore must be maintained at a certain level. Oxidation processes are responsible for the thermoregulation process, and, therefore, the body constantly needs oxygen.
The same Ivan Sanderson mentions that before diving to the bottom, the shellfish collectors from Senegal ate something, quite likely a certain product that allows you to saturate the blood with oxygen. Another explanation is associated with the presence of a special natural atavism in humans - oxygen-free oxidation, due to which, for example, cetaceans are able to stay under water for a long time without air. It is quite possible that it is these factors that explain most of the legends about people - ichthyandras.