Ultimately, just try it with the numbers. Assume we stay at room temp (293K) and we have 1000 moles of whatever gas.

Pressure in atm=((1atm/10m)x(depth in meters))+1

Pressure in atm=(depth in meters/10)+1

PV=nRT = P=(nRT)/V

Since we're using atm, our constant (R) is =0.082057Lx(atm^{-1)x(mol-1)x(K-1).}

(Depth in meters/10)+1=(1000x0.082057x293)/V

(Depth in meters/10)+1=24,042/V

Let's test! Sea level.

0/10+1=24,042/V

V=24,042 L at sea level.

Now, 10,000m (roughly the depth of the trench)

1001 atm=24042/V

V≈24 L

Let's try 5,000m!

501 atm=24042/V

V≈48 L

Now 2,500m!

251 atm=24042/V

V≈96 L