These two lines are similar in meaning and emphasize the response of the surrounding people to the destruction of Tyre. (See: [[rc://en/ta/man/jit/figs-parallelism]])
Here "the coasts" represents the people living there. Alternate translation: "Now the people of the coastlands tremble" (See: [[rc://en/ta/man/jit/figs-metonymy]])
Here "the islands in the sea" represents the people living there. Alternate translation: "The people of the islands are terrified" (See: [[rc://en/ta/man/jit/figs-metonymy]])
The destruction of Tyre is spoken of as if it was a person who had died. Alternate translation: "you have departed" or "you exist no more" (See: [[rc://en/ta/man/jit/figs-personification]])