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。
2
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。
3
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.