How to say"海洋已死,世界已死"in English?

the sea has died,the world has died (这样说是尊重断句的需要）
其实也可以这样说：
The sea has died, so has the world. （海洋已死，世界也一样）

加了both的话，就是
both the sea and the world have died

楼上的has 和 been 用错了

The sea and the world are both died.

Both sea and world are dead!

it's better to use "as well" in this case:

The ocean's dead, the world would be dead as well.

Both Ocean and world have been dead

Both the ocean and the world has been died