coastline本身就是一个英文单词，意思是：n.海岸线;海岸地形(或轮廓);沿海地带。

例句：

1. The coastline is being eaten away year by year.

海岸线年复一年地被侵蚀着。

2.The road follows the natural contours of the coastline.

这条路沿着海岸线的自然轮廓延伸。

3.Sri Lanka is again rebuffing diplomatic calls for an immediate halt to its final assault against Tamil rebels, on a sliver of northeastern coastline.

斯里兰卡有一次断然拒绝了外交方面对其立即停止对塔米尔叛民的攻击的要求。塔米尔人居住在东北沿海的狭长地带上。