lagoon /(lȧ*go͡on")/

la·goon

lagoon

n.
  1. A shallow sound, channel, pond, or lake, especially one into which the sea flows; as, the lagoons of Venice.
  2. A lake in a coral island, often occupying a large portion of its area, and usually communicating with the sea. See Atoll.

Phrases & Compounds
Lagoon island
a coral island consisting of a narrow reef encircling a lagoon.