.is off the coast of Australia.

离开...,隔着...;在(离岸边不远的)海面
off the coast:在海面上
Examples:
1.They had been wrecked (ie shipwrecked) off the coast of Africa.
他们的船在非洲沿海遇难损毁.
2.After months of drilling,oil was found off the coast.
经数月钻探,在沿海找到了石油.
3.I look at Cuba,ninety miles off the coast of the United States.
看看古巴,它离美国沿海仅九十英里.
4.It is a lone island off the coast of Guangdong,a mere dot,so to speak,in the South China Sea.
它是广东海岸边的一座孤岛,可说是南海上的一个小点.
这个是词典查的,你可以通过这个地址看off的所有意思.