He hears the echo of the wave reflected from the ocean floor directly below 6.0 s later. How deep is the ocean?

A sailor strikes the side of his ship just below the surface of the sea. He hears the echo of the wave reflected from the ocean floor directly below 6.0 s later. How deep is the ocean at this point? (Note: Use the bulk modulus method to determine the speed of sound in this fluid, rather than using a tabluated value.)