I turn a glass upside down, trap the air in it by putting it in water, and then I take the glass down to 10 metres/33 feet. The air space would

Question

become half the size it was at the surface.
not change in size.
become 1/3 the size it was at the surface.
become 2/3 the size it was at the surface.

Answer 1

become 1/3 the size it was at the surface.

Answer 2

If I am not able to equalize (clear) my body air spaces, it may be because I have
seasickness.
heart disease and high blood pressure.
a cold, allergy or another medical problem.
anxiety.

Answer 3

a cold, allergy or another medical problem.

Answer 4

If my ears or sinuses hurt while I am descending (going down), it usually means
my air spaces are equalized.
my mask strap is too tight.
I am feeling a squeeze and need to equalize.
my mask is too small.

Answer 5

I am feeling a squeeze and need to equalize.