Wikipedia and the scientific community
The diving reflex
All mammals have an automatic response to being submerged in (or falling into) water known as the 'diving reflex'. This autonomic reaction immediately ensures the animal holds its breath, reduces its heartbeat (bradycardia) and redirects oxygen laden blood to the brain and the most oxygen dependent organs (vasoconstriction). In fact, so effective is this mechanism, that a person or an animal doesn't even need to be fully submerged for it to take effect; it works just as effectively when the face is submerged or cold water is splashed on the forehead and around the eyes and nose. In Darwinian terms, this evolutionary adaptation makes sense, as it means any animal that falls into water won't immediately drown. Comparisons with other animals have shown that the diving reflex is more highly developed in aquatic and semi-aquatic mammals, as one would expect, and that human test subjects fared only slightly better than most terrestrial animals until further tests showed there was a big difference when volunteers who had had some previous breath holding training were used instead:
It should be noted that 'training' can be aquired by anyone in a very short time. All it takes is up to five breath holds spaced out by three minute intervals to establish a difference to our physiological response to submergence, and breath-holding could be prolonged by 160%. 
Breath holding abilities
Newborn human babies are born with an automatic breath-holding reflex, which is why they can be immersed in water as soon as they are born. In baby swim classes, parents are usually encouraged to wet their baby's face before immersing them in order to activate the diving reflex. The breath-holding reflex, unlike the diving reflex, is generally lost if the infant is not introduced to water within the first 6-10 months, and has to be relearned.
Many non-aquatic mammal species can hold their breaths underwater if they are forced to, but they cannot voluntarily hold their breaths on a whim, as we can, although better studies are needed to confirm this.  Compared to terrestrial mammals, human beings do have superior breath-holding abilities. Erika Schagatay from the Department of Technology and Sustainable Development and Swedish Winter Sports Research Centre, has spent over twenty years researching human breath holding abilities among diving peoples around the world, including the Ama in Japan, the Hae Nyo in Korea and the Sea Nomads or Sea Gypsies in Indonesia, Phillipines and Burma. Her observations have led her to conclude:
Aquatic and semi aquatic mammals obviously have highly developed breath-holding abilities. Like them, and just like semi-aquatic birds or reptiles, we can override the signals to our brain that carbon dioxide is building in the blood and continue holding our breath for a varying amount of time according to our training and experience. Among all air-breathing animals, the record is held by the sperm whale which has been known to hold its breath for deep sea dives for up to ninety minutes, although they regularly dive for 20-30 minutes each time. Experiments with seals and porpoises have shown that they can be trained to dive and retrieve objects at different depths, and that they can calculate how long they need to hold their breath for according to the item that they are being asked to retrieve, consciously making a decision before they dive about how long they need to hold their breaths for. We also calculate how much oxygen we need on a single breath as this is something we do every day, whether we enter the water or not. Our breath holding abilities are a prerequisite for speech and song. We automatically control the amount of breath we need to utter a sentence or sing. The majority of terrestrial animals cannot do this and it is one of the reasons why they cannot speak 
Although we cannot hope to compete with the fully aquatic cetaceans, or even the almost fully-aquatic pinnipeds (seals, sealions, etc.), Erika Schagatay has spent enough time as a diving instructor studying free diving peoples that she notes we can compete quite well with several semi-aquatic species:
In recent decades we have seen an increase in the number and variety of human apneic diving competitions including maximum duration or depth on a single breath, either with or without fins and/or weights. The world record for no limits apnea free-diving for men was set by Herbert Nitsch from Austria in 2007 at 214 meters on a single breath, and by Tanya Streeter, USA, at 160 meters for women in 2002. The record for static apnea (holding one's breath under water while remaining still) is held by Stephane Mifsud from France (11 minutes, 35 seconds) for men, and by Natalia Molchanova, Russia, ( 09 minutes, 2 seconds) for women, "performances in the range of marine mammals," Schagatay says.
Schagatay goes on to observe that the comparatively high age at which top results can be produced by competitive divers is atypical compared to other sports. (Natalia Molchanova was 53 years old when she tragically failed to surface from a deep dive in summer 2015.) Many Ama divers also remain fully active into their 90s. She notes that marine mammals are known for long life-spans not often seen in typical land dwellers.
However, nobody is suggesting that the ancestors of homo typically swam to depths of 100 meters or more, or needed to hold their breaths for such long periods on a daily basis. Human ancestors would probably have spent much of their time harvest-diving for shell-fish and edible plants, or perhaps spear fishing.
1. Morgan, Elaine. The Aquatic Ape Hypothesis. Souvenir Press. p.144
|Website: F. Mansfield, 2015|
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