The “Iron Rice Bowl” and Economic Reform: The primary meaning of `下海` is inseparable from China's 改革开放 (gǎigé kāifàng), the “Reform and Opening Up” period that began in the late 1970s. Before this, most urban workers held positions in state-owned enterprises (SOEs) or government bureaus. This system was known as the 铁饭碗 (tiě fànwǎn), or “iron rice bowl,” because it guaranteed a job for life, along with housing, healthcare, and a pension. It was incredibly secure, but also rigid and offered little room for personal ambition.
`下海` describes the act of smashing one's own iron rice bowl. People who “plunged into the sea” in the 80s and 90s were seen as pioneers and risk-takers. They were giving up total security for the unknown potential of wealth in the new market economy.
Comparison to Western Culture: The closest Western concept is “quitting your 9-to-5 to launch a startup.” However, the stakes were much higher for those who `下海`. It wasn't just changing jobs; it was leaving an entire social and economic system for another. The risk was not just financial failure, but the loss of a complete social safety net provided by the state, or `体制内 (tǐzhì nèi)`. The decision was therefore more dramatic and culturally significant.
The Slang Meaning: The slang usage for entering prostitution borrows the central metaphor of entering a dangerous and socially “murky” world for financial gain. It's a cynical application of the same concept, highlighting a darker side of the economic boom. This meaning is highly informal and pejorative.