Gulf and Lagoon

Gulf noun - A part of a body of water that extends beyond the general shoreline.

Lagoon and gulf are semantically related in nature topic. In some cases you can use "Lagoon" instead a noun "Gulf", when it comes to topics like body of water.

Lagoon noun - A body of water cut off from a larger body by a reef of sand or coral.

Gulf and lagoon are semantically related in body of water topic. You can use "Gulf" instead a noun "Lagoon", if it concerns topics such as shallow body of water.