Sight and hearing are important in oceanography because we can use them to find out many different things about the oceans.
I learned using my hearing that humpback whales make sounds that travel over long distances for communication. The deep sea is not completely silent, you can hear the currents and animals moving around. Seagulls constantly call to each other while looking for fish. You can hear the waves coming in and then retreating back to the sea in a regular sound pattern. In a storm, the sounds of rain and wind dominate, broken occasionally by the clap of thunder.
Looking at the coral reefs, I learned that most of them have regular patterns with lots of fish swimming around, seeking food and shelter in schools or by themselves.
Our senses are important for us to learn about the ocean. Other senses we can use in our observations are smell, touch, sometimes even taste.