1. Coral reefs are delicate ecosystems that provide a habitat for a wide variety of marine life.
珊瑚礁是一个脆弱的生态系统，为各种海洋生物提供了栖息地。

2. The diver marveled at the vibrant colors of the coral beneath the ocean's surface.
潜水员对海洋表面下的珊瑚的鲜艳颜色感到惊叹。