水上警察

例句：

1. 1. The police are investigating the incident in the river.
   警方正在调查河里的事件。
2. 2. The water police patrol the lake every evening.
   水上警察每晚在湖上巡逻。
3. 3. The water police have been helping to clean up the polluted water.
   水上警察一直在帮助清理污染的水。