Dangerous undertows make swimming unsafe along most of the coastline.

由于存在着危险的下层逆流，在大部分海岸线附近游泳都不安全。

In some places swimmers may encounter strong undertows or ocean currents.

在一些地方游泳者可能遇到强势的暗流或者洋流。

Unless this is flooding the shore, all this water is somehow returning to the ocean. There are a couple of ways it can do this: undertows and riptides.

除非淹没海岸，所有的水终将以某种方式回到大海之中——潜流或者激流。