A ship searching for a sunken ship sent a sonar signal and detected an echo after 5 s. If ultrasonic wave travels at 1525 ms⁻¹ in seawater, approximately how far down in the ocean is the wreckage of the sunken ship located?

The echo time of 5 s includes the journey of the ultrasonic wave to the wreckage and back. Therefore, the depth is:

$$d = \frac{vt}{2}$$

$$= \frac{1525 \times 5}{2} = 3812.5 \text{ m}$$

Hence, the wreckage of the sunken ship is located approximately 3812.5 m (about 3.8 km) below the ocean surface.