Comment by OxO4
2 days ago
Freedivers are also taught not to exhale underwater, because it wastes oxygen and lowers your CO2 level, making it harder to know when you actually have to come back up. Your body can't sense the level of oxygen it has, so freedivers rely on CO2 levels as a proxy, so messing with it is dangerous.
And you also becoming much less buoyant and will not surface without actively swimming or pulling the line.