A shoal of fish will do this.

鱼群也会反射声音的.

7-9. So it is a comparatively simple step from locating the sea bottom to locating a shoal of fish.

因此，从测定海底深度到测定鱼群的位置这一进展相对较易。

Humpbacks release bubbles to surround and confuse a shoal of fish. They can also frighten them with sound.

座头鲸释出气泡围住鱼群并使之迷惑。它们也能使用声音吓住鱼群。