Water hazard is a term used to describe a potential danger posed by water. A REEF is a type of underwater formation, usually made up of coral, rocks, or sand, that can be hazardous to ships and other vessels. An ORCA is a type of large, predatory whale that can pose a danger to humans and other animals in the water. An ICEBERG is a large mass of ice that can be dangerous to ships and other vessels due to its size and unpredictability.