How far away are the fish?

Question

A sound pulse emitted underwater reflects off a school of fish and is detected at the same place 0.23 s

 later (see the figure below). How far away are the fish? (Assume the water temperature is 20°C.)

Answer 1

I find that the speed of sound in water at 20 °C is about 1481 m/s. In 0.23 s sound travels distance d = vt = 340.6 m, but this is round trip, so the distance to the fish is 170 m.