The pressure 15.0 m under water is 248 kPa.
What is this pressure in bar?

The answer is rounded to three sig figs. (2.45 atm to be exact)

Explanation:

The thing to remember about an atmosphere is that it represents the average pressure exerted by the atmosphere at sea level.

You know that pressure is defined as force per unit of surface. When you have a force of 1 N pushing on a surface of  1m ^ 2, you have a pressure of 1 pascal, or 1 Pa.

When you have exactly  1000 Pa , you have one kilopascal, or  kPa .

In order to have a pressure of  1 atmosphere, or  1 atm , you need to have exactly  101.325 kPa . This means that the pressure given to you will be equivalent to

248 kPa* 1 atm/101.325 kPa = 2.45 atm

(cancel out the kPa in the equation)