The volume of gas in a flexible container at a depth of 10 m/33 ft will expand to its original volume if taken to the surface.

Twice its original volume.

Explanation:

For diving applications, 10 m/33 feet of sea water is taken to exerts a gauge pressure that is the same pressure as the atmosphere, or one ata/bar.

This means that we add one ata/bar pressure for every 10 m/33 feet you descend.

The effect of this is that, at 10 m/33 ft, you're under an absolute pressure of two ata/bar, one from air and one from water. Adding another 10 m/33 ft to this depth to make it 20 m/66 ft, puts you under under three ata/bar of pressure and so on.

Descending to a depth of 10 m/33 ft, with a flexible container means that you have double the ata/bar pressure acting on you. If you decide to resurface, the pressure on the flexible container will reduce by a factor of two.

Since volume is inversely proportional to the pressure, if the pressure reduces by a factor of 2, then the volume will increase by a factor of two, or we can say that the volume will double.

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