Baking soda and vinegar react because of an acid-base reaction. The product of this creates carbon dioxide.
First, we convert the depth of the water into meters. This is:
60 feet = 18.3 meters
Now, we compute the additional pressure exerted due to the water, which is given by:
Pressure = density * gravitational field strength * height
P = 1000 * 9.81 * 18.3
P = 179.5 kPa
The atmosphere pressure is 101.325 kPa
The pressure of the gas bubbles 60 feet under water will be:
179.5 + 101.325 = 280.825 kPa
The pressure at the surface of the water will be equal to the atmospheric pressure, 101.325 kPa.
Because of this decrease in external pressure as gas bubbles rise, they are seen to expand.