adjective
oceanic
oh-shee-AN-ik/ˌəʊʃiˈænɪk/
Relating to or resembling the ocean.
The tiny research vessel crosses a vast expanse of oceanic water.

Etymology
The ocean's Greek ancestor named a great sea encircling the earth, linking the word with vastness. Oceanic, probably from French océanique, describes either the sea or something resembling its immensity.
In context
researchers and oceanographers however conduct studies to better understand these mysterious creatures and their role in the oceanic ecosystem
More examples
- Scientists track changes in oceanic temperatures.
- These birds spend most of their lives in oceanic waters.
- The desert stretches before us in an oceanic expanse.
Forms
ocean noun — The vast body of saltwater covering Earth.