Ask HN: Is it possible to blow up a balloon while you’re under water?

First search result: <a href="https:&#x2F;&#x2F;van.physics.illinois.edu&#x2F;qa&#x2F;listing.php?id=14253&amp;t=is-it-possible-to-inflate-a-balloon-with-air-underwater" rel="nofollow">https:&#x2F;&#x2F;van.physics.illinois.edu&#x2F;qa&#x2F;listing.php?id=14253&amp;t=i...</a><p>Consider using search engines in the future.

Depends on the air-pressure in the lungs. If you inflate them from a scuba tank, possibly. If you take a breath and then jump in the water, no.