The theme of World Ocean Day, 2021 is "The Ocean: Life and Livelihoods". This option highlights the importance of the ocean not only in sustaining life but also in providing livelihoods for communities around the world. By choosing this theme, the focus is on the interconnectedness of the ocean with various aspects of human life. It emphasizes the significance of the ocean as a source of food, jobs, and economic opportunities.

Option 1, "Innovation for a Sustainable Ocean", may seem like a plausible theme, but it is not the correct answer. While innovation is indeed important for a sustainable ocean, this specific theme was not chosen for World Ocean Day, 2021.

Option 3, "Gender and Oceans", although relevant in highlighting the role of gender in ocean-related issues, is not the chosen theme of World Ocean Day, 2021.

Option 4, "Clean Our Oceans", focuses on the vital task of cleaning the oceans but is not the specific theme for this year`s celebration.

It is important to remember that the theme of World Ocean Day may vary each year, highlighting different aspects of our relationship with the ocean.