The average person can hold their breath for up to a minute.
According to the Guinness World Records, the longest any human has held the breath is 18 minutes and 7 seconds! However, most people find it difficult to imagine an eternity in these circumstances. So we recommend holding your breath for no more than 2 minutes at a time.
The trick is not so much to have loads of physical strength but rather mental focus which helps prevent carbon dioxide from accumulating in your blood due to hyperventilation caused (usually) during periods of high stress. In other words, you need only sustain a level breathing pattern and use it as practice before diving into deep waters when fear or panic might knock out some people…or make them black out.