Tidal Islands - Tidal islands are extremely similar to continental islands, except land attaching the island to the mainland, has not fully eroded. Instead the land is under the ocean surface, at high tide.

Barrier Islands - Certain barrier islands form, influenced by the most recent ice age. Glaciers melting, results with sea levels rising around sand dunes, creating sandy islands. 

Oceanic Islands - Oceanic islands form when volcanoes erupt underwater. Layers of magma builds up. During this process the volcano is called a seamount. Overtime the volcano builds reaching the ocean surface, forming an island.

Coral Islands - Coral islands are low islands formed from sea animals called corals. Corals create an external skeleton of calcium carbonate, which grows into a thick layer of a seafloor. Overtime the coral reefs break the water surface, forming coral islands.

Artificial Islands - Artificial islands are man-made. Usually created to expand an section of an existing island, creating extra land for agriculture.