Expansion:
As a gas decreases in pressure, it will increase in volume. When it is held in a flexible medium, that will get larger.
In this case, it was the pores in neoprene for a diving hood here at work.
The divers are working at 700 feet of water, and the hood was brought from that pressure (318.5 PSI) to the surface (14.7 psi) in about 20 seconds.
Here is the result compared to the new hood:
By bigredtruck at 2012-03-16
It came out through a med-lock where the operation of is shown in the link below. I shot this video just the other day.