system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What is dry drowning, and how does it happen?
gpt
I posted this in response to the top comment as their explanation was incorrect but just making a separate post to provide an answer to your question. 

Your vocal cords, which sit at the top of your airway, are quite sensitive. In dry drowning, water hits the vocal cords which causes spasm - otherwise known as laryngospasm. In basic terms, the vocal cords snap shut in a protective reflex which seals off the airway and lungs. In reality, the victim suffocates rather than drowns - no water enters the lungs. 

Many people here are describing secondary drowning, which is an inflammatory condition caused by water entering the lungs and causing irritation. Fluid build up occurs within the inflammatory response causing pulmonary oedema, or fluid filled lungs. 

To confuse things however, laryngospasm can also cause pulmonary oedema. Our breathing works via negative pressure - when we open our rib cage, that stretches the lungs open and creates a small vacuum causing air to rush in. This is how we breathe - we don't 'suck' air in per se, we create a negative pressure environment with the muscles in our rib cage and diaphragm and air rushes in to equalise pressure between our lungs and the external environment. 

When laryngospasm occurs, the victim may still be using all of those muscles to try to breathe but their airway is sealed shut. So, they are creating a negative pressure environment in their lungs, but with no way for air to get in to equalise the pressure. The victim then ends up drawing fluid from their tissues into their lungs instead, resulting in pulmonary oedema, or fluid filled lungs.