On January 23, 1960, Swiss engineer Jacques Piccard and U.S. Navy officer Don Walsh made history by descending in the bathyscaphe Trieste to the deepest known point in the ocean—the Mariana Trench. Their dive reached nearly 11,000 meters (about 36,000 feet) below the surface, a depth where water pressure is immense, equivalent to about 16,000 pounds per square inch. The Trieste was a specially designed submersible with a thick, steel spherical cabin, built to withstand these extreme pressures. During the five-hour descent, a crack was heard in one of the plexiglass viewports at around 9,000 meters, but the explorers continued their mission, relying on the vessel’s robust design. To descend and ascend safely, the Trieste was equipped with nine metric tons of magnetic iron balls that acted as ballast. Electromagnets held these balls in place, and they were released automatically in case of electrical failure. This system allowed the submersible to manage its depth effectively in the crushing environment of the deep sea. After nearly five hours of descent, the Trieste reached the Challenger Deep, the deepest part of the Mariana Trench. Upon landing, a cloud of sediment obscured visibility, but the explorers were able to spot life forms, including a fish, red shrimp, and an unknown species of flat fish. These discoveries challenged the prevailing belief known as the "azoic depths" theory, which suggested that no life could exist at such extreme depths. The explorers spent about twenty minutes at the bottom, conducting observations of the water’s temperature, radioactivity, and other characteristics. To return to the surface, they released the iron ballast in one-ton increments, allowing the Trieste to rise slowly. They resurfaced at 16:56, completing the dive in 8 hours and 33 minutes. This historic expedition significantly advanced scientific understanding of life in the deep ocean. For decades, no one attempted a dive to such depths until 2012, when filmmaker James Cameron descended in the Deepsea Challenger. More recently, in 2020, China's Fendouzhe and the DSV Limiting Factor (between 2019 and 2022) also reached the Challenger Deep, continuing the legacy of the Trieste’s pioneering journey.