Answer: The correct answer for the blank is - Oceanography.
Oceanography ( also known as oceanology) can be described as the study of all aspects of ocean that includes physical, biological, and chemical properties.
It is a part of earth science, which covers a large range of areas, including ecosystem dynamics; waves, ocean currents, geology of seafloor etc.
In the question, the subject wants to learn about the deep blue oceans, thus, he wants to study oceanography.
