hydrometra

例句：

1. 1. The jellyfish is a common sight in the ocean.
   水母是海洋中的常见生物。
2. 2. Hydrometra was discovered by scientists who were studying underwater creatures.
   科学家发现了水母，他们正在研究水下生物。
3. 3. The hydrometra has a unique ability to change color and shape to blend in with its surroundings.
   水母具有独特的变色和变形能力，以适应周围环境。