A shoal of fish will do this.

鱼群也反射声音。

Wherever they went, sailors kept scrupulous logs, detailing narrows and shoals for future adventurers.

无论走到哪里，水手们都会一丝不苟地记录下日志，为未来的冒险者详细描述狭窄的水域和浅滩。

This will give some idea of the havoc it makes among shoals of fish.

由这想而知，它如何肆意蹂躏浅滩的鱼类的。

It's these shoals that support most of the world's sea mammals.

鱼群也养育了世界大多数海洋哺乳动物。

Thirty miles away, shoals of squid are jetting upwards towards the surface.

30英里外的海，大量的鱿鱼游到海面。

Reaching speeds of up to 20mph, Puck's son India chases the shoal towards the shore.

因迪亚时速高达每小时 20 英里，赶着鱼群往岸边去了。

Species like redeye piranhas are more solitary, while red-bellied piranhas form shoals of 10 to 100.

像黑食人鱼倾向于单独行动，而红腹食人鱼会形成 10 到 100 条的鱼群。

Larger, mature red-bellied piranhas tend to assume privileged positions at the shoal's center, where it's safest.

体型更大、更成熟的红腹食人鱼经常待在群落的中心；那里最为安全。

He swam above the fish shoal, and then...he slapped the water, killing or stunning the fish.

鲸鱼游到鱼群方，然后拍打水流将鱼杀死或击昏。

This group is led by Mr Zhang, an expert in tracking down shoals of bighead carp.

这一队的队长张先生，追踪胖头鱼群的行家里手。

Squid, which can be found mainly in estuarine, deep-sea, and open-water habitats, often swim together in shoals.

乌贼，主要分布在河口，深海和开阔水域的栖息地，经常在浅滩游泳。

This gulfweed, the swimming gulfweed or berry carrier, is the chief substance making up this immense shoal.

这海藻浮水藻，或承湾藻，主要构成这广大的草叶海面。

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

从测定海深到测定鱼群，这一进展比较容易。

First it was dark as a shoal in the blue water that was more than a mile deep.

起先，这摊血黑魆魆的，如同这一英里多深的蓝色海水中的一块礁石。

Alas, merely observing a shoal does not make it clear which individuals lead and which follow.

然而，仅仅只观察一个鱼群并不能清楚地区分哪个领导，哪个随从。

Most recently, he has modelled the behaviour of shoals of fish.

最近，建立了鱼群行为模型。

By contrast, the baleen whales the researchers looked at, once they have encountered a shoal of prey, are in nutritional nirvana.

相比之下，研究人员观察到的须鲸一旦遇到一群猎物，就处于营养极乐世界。

He is now making a robot predator to see how the shoal reacts to less benign intruders.

现在正在制作一个机器猎食者，用来观察鱼群对凶猛入侵者的反应。

That is a start. But real shoals do not exist to swim in circles.

那只一个开始。不过真实的鱼群并不只转圈游动。

These morphing shallows of sand and sediment are known as shoals.

这些变化莫测的沙石浅滩被称为沙洲。