3 sentences

1. 这里的河水水流湍急，游泳非常危险。

   zhè​lǐ de hé​shuǐ shuǐ​liú tuān​jí, yóu​yǒng fēi​cháng wēi​xiǎn.

   The river current here is very swift, so swimming is very dangerous.

   Source: Dong Chinese Dictionary

2. 山上的溪流湍急，非常适合进行漂流运动。

   shān​shàng de xī​liú tuān​jí, fēi​cháng shì​hé jìn​xíng piāo​liú yùn​dòng.

   The mountain streams are rapid and very suitable for white-water rafting.

   Source: Dong Chinese Dictionary

3. 这两条河流在山脚下交汇，随后水流变得更加湍急。

   zhè liǎng tiáo hé​liú zài shān​jiǎo xià jiāo​huì, suí​hòu shuǐ​liú biàn de gèng​jiā tuān​jí.

   The two rivers meet at the foot of the mountain, after which the current becomes more rapid.

   Source: Dong Chinese Dictionary