鲨鱼 is the Chinese word for "shark," combining 鲨 (shark) with 鱼 (fish). Like many animal names in Chinese, it uses the category character 鱼 to indicate it is a type of fish. It is used in both everyday and scientific contexts.
我在海里看到了一条鲨鱼。
Wǒ zài hǎi lǐ kàn dào le yī tiáo shāyú.
I saw a shark in the sea.
鲨鱼是海洋里的顶级捕食者。
Shāyú shì hǎiyáng lǐ de dǐngjí bǔshí zhě.
Sharks are the top predators in the ocean.
这部纪录片讲的是鲨鱼的生活。
Zhè bù jìlùpiàn jiǎng de shì shāyú de shēnghuó.
This documentary is about the life of sharks.