Answer :
(a) The pressure at this depth is, 1.6 atm
(b) The depth of the snorkeler is, 6 meter.
Explanation :
Boyle's Law : It is defined as the pressure of the gas is inversely proportional to the volume of the gas at constant temperature and number of moles.

or,

where,
= initial pressure = 1.0 atm
= final pressure = ?
= initial volume = 14 mL
= final volume = 8.5 mL
Now put all the given values in the above equation, we get:


The pressure at this depth is, 1.6 atm
Now we have to calculate the depth of the snorkeler.
Let the depth of the snorkeler be 'x'.
As per question,
1.6 atm - 1 atm = x meter
0.6 atm = x meter
and,
As, 1 atm = 10 meter
So, 0.6 atm = 6 meter
The depth of the snorkeler is, 6 meter.