Approximately 71% of the Earth's surface is covered by the ocean. This means that the oceans encompass a significant majority of our planet's surface area. The remaining 29% includes continents, islands, and other landmasses. It's important to note that this percentage can vary slightly depending on factors such as the measurement criteria used and the definition of what constitutes an ocean (including marginal seas and other bodies of saltwater). However, the general estimate is that oceans cover about 71% of the Earth's surface.