下海 as 'going into business' became hugely popular during Deng Xiaoping's economic reforms in the 1980s-90s. Millions of people
下海 — quit their
铁饭碗 ('iron rice bowl,' guaranteed government jobs) to start businesses. The metaphor frames entrepreneurship as diving into a dangerous but opportunity-filled ocean. Many of China's billionaires are members of this '
下海 generation.'