A long line of jagged rock, coral, or sand just above or below the surface of the ocean. An artificial reef is when a human-made structure creates a reef on the sea floor.

A boat that is being used to take a group of people on a particular 'expedition' or journey.

A very large ocean wave which is usually caused by a volcanic eruption, undersea earthquake, or landslide. It can travel hundreds of kilometres over the open sea and cause a lot of damage when it hits land. Also called a tidal wave.

An area that is legally protected from activities that remove plants/animals or alter their habitat, unless it is being done for scientific purposes. Swimming, boating, and scuba diving are usually allowed in marine reserves, but not activities such as fishing, dredging, or mining.

A type of requiem shark found worldwide. The shark likes living on clear reefs around islands and The International Union for Conservation of Nature (IUCN) has defined this shark as near threatened.