Low islands

Low Island Geographically is an island of coral origin. The Term applies whether the island was formed as a result of Sedimentation upon a Coral reef or the uplifting of those kind of islands the term is used to distinguish those kind of islands from high islands, whose origins are volcanic

The Moruroa atoll, composed of low islands on the reef encircling a central lagoon

References

Map of Niue, a low island and former ring-shaped island formed of coral, where reef and lagoon have risen above sea level due to uplifting