Material: sea water speed of sound (m/s) 1533
an anchored fishing boat uses sonar to work out how deep the sea is. it sends out a ping sound and detects the echo 2 seconds later.
how deep is the water?

If the echo is detected 2 seconds after the ping is transmitted,
then the sound has traveled

           (2 sec) x (1533 meter/sec) = 3,066 meters.

But the sound had to travel down from the boat to the bottom, then
get reflected, then travel up from the bottom to the boat.  So the
sound actually traveled a distance equal to double the depth.

The depth is  (1/2) (3,066 meters) = 1,533 meters .
                                               (about 5,030 feet)