Final answer:
Submersibles and ROVs equipped with advanced technology have explored the abyssal zone of the ocean, uncovering a unique ecosystem around hydrothermal vents sustained by chemosynthetic bacteria, alongside historical methods like the fathom for measuring ocean depths.
Step-by-step explanation:
The exploration of the ocean's deepest parts, such as the abyssal zone, has revealed a unique ecosystem. The abyssal zone, reaching depths of 4000 m or greater, is characterized by very high pressure, very low temperatures, and varying reports on oxygen and nutrient content. Despite these harsh conditions, a variety of invertebrates and fish have been found. Notably absent are photosynthetic organisms, as no light penetrates to such depths. However, hydrothermal vents in the abyssal zone support life through chemosynthetic bacteria, which use hydrogen sulfide and other minerals as an energy source, thus forming the basis of a deep-sea food chain.
In historical context, before modern electronics, sailors used the fathom—a unit of length equal to six feet—to measure ocean depths with a knotted rope. Nowadays, we employ sophisticated instruments to determine sea floor depth with precision. These methods have significantly contributed to our understanding of maritime history and underwater geological features, such as coral reefs and shipwrecks.
Exploration to these depths has typically been facilitated by submersibles and remotely-operated vehicles (ROVs) equipped with advanced tools for probing the deep sea and studying underwater life forms and geological formations.