英语听力：自然百科 海洋天堂大堡礁:堡礁内外—3（在线收听）

 -It's all exciting to see a large animal in the sea, and of course, the turtles are very iconic species in marine world. And I'm surrounded around this life. Hundreds and hundreds of turtles are in the water column above me, passing over the reef's crest and now in the blue water.The turtles all converge on small islands made of coral rock and sand, known as the coral cases, but not all are suitable for nesting. Some only are sank down, exposed only in low water. And many others have beaches that swamp to high tide. Islands with deep sand and covered in vegatation are more stable, and one island in particular seems just right. In the far north of the Great Barrier Reef is the Rain Island. It's so wide and so special that few people are permitted to land. It's one of the most protected islands on earth. This speck in the ocean is barely a kilometer long. Yet it attracts thousands of turtles and enormous flocks of sea birds.