why is it so difficult to breathe when snorkeling at a depth of 1 meter?

Answer 1

because you're breathing.

seriously.

like the guy above me said,
water pressure pushes on
your torso from all sides making
it harder to breathe beacuse it
takes more energy to keep your
chest at its normal dimensions
instead of being compacted.

so when the water pushes in
on your chest, it forces air out,
of it, via the lungs and airway,
and makes it harder for you to
pull it back in. thus the difficulty
breathing.

Answer 2

It's because of the water pressure on your chest. At a depth of 1 meter, you have an extra 1.4 pounds pushing on every square inch of your chest. So when you breathe, it's like trying to lift that weight off your chest.

Answer 3

Water pressure.