The oceans cover nearly 70% of Earth's surface, yet they are largely unexplored. The amount of time that it would take to explore such a vast region is one of the reasons that the oceans have not been well explored.
The deepest part of the ocean was recorded in 2010 by the United States Center for Coastal and Ocean Mapping. The depth was nearly 11,000 meters! The water pressure at such depths is extreme due to the pull of gravity on all of the water that resides above such depths. This poses a challenge as it is difficult to create equipment that can withstand such pressures. Also, little sunlight can reach such depths. This poses another difficulty for exploration.
Additionally, ocean tides and currents are forever changing and shifting the ocean floor. This makes it difficult to pinpoint and relocate discoveries.