There's a flood dragon under the long bridge over that river.

河上的长桥下面有一条蛟龙。

youdao

It is like a long dragon, it makes a rumble sound when it walks. it will run on a iron bridge when come across a river and drill cave when come across a mountain.

长长一条龙，走路轰隆隆，遇水过铁桥，遇山钻山洞。

youdao