Deep-sea and Oceangoing

Deep-sea adjective - Of, relating to, or occurring in the open sea.

Oceangoing and deep-sea are semantically related in sea topic. In some cases you can use "Oceangoing" instead an adjective phrase "Deep-sea", when it comes to topics like marine, nautical, concerning the sea.

Oceangoing adjective - Used on the high seas.

Deep-sea and oceangoing are semantically related in sea topic. You can use "Deep-sea" instead an adjective "Oceangoing", if it concerns topics such as marine, nautical, concerning the sea.