The Earth's oceans cover more than 70% of the planet's surface, yet much of their mysterious depths remain unexplored. When describing the ocean, it is useful to break the sea up into regions by levels of depth, from the surface to the bottom. These sections are known as Pelagic Zones. The word pelagic is derived from ancient Greek meaning 'open sea'. Conditions in the ocean change with depth: pressure increases; temperature and light decrease; salinity, oxygen, and micronutrients all change as well. There are five different Pelagic layers encompassing all open waters beyond the coastal regions. Each zone presents unique environments for life on earth, but also challenges for exploration due to their vastness and inaccessibility. The development and utilization of submersibles has revolutionized our understanding of these aquatic realms, and has helped us in unraveling the mysteries of each pelagic zone.