海王 (hǎi wáng) literally means 'sea king' — Poseidon, Neptune, or the DC superhero Aquaman. In internet slang, it refers to someone who juggles multiple romantic interests at the same time, 'casting a wide net' like a king ruling over the entire ocean. The term is mostly aimed at men but increasingly used for women too. The extended metaphor is rich: a 海王's collection of romantic targets is a 鱼塘 (fish pond), maintaining multiple flirtations is called 养鱼 (raising fish), and each person being strung along is a 鱼 (fish).

It depends on context. Used as an accusation — '他就是个海王' (he's a total sea king) — it's clearly negative, implying someone is dishonest about their romantic intentions. But it's also widely used as playful self-deprecation or teasing among friends, like captioning a selfie '海王出巡' (the sea king on patrol). It's milder than 渣男 (scum man), which implies deliberately causing emotional harm. A 海王 might just be keeping options open; a 渣男 is actively hurting people.

The DC movie Aquaman (《海王》) hit Chinese cinemas in December 2018 and grossed over $290 million domestically. The slang meaning emerged in early 2019, building on an older meme — 鱼塘 (fish pond) was already slang for someone's roster of romantic interests, from a drama line by actor Zhang Han. In March 2019, the Douyin audio '本以为游进了哥哥的鱼塘，没想到哥哥是个海王' (I thought I'd swum into his fish pond, turns out he's a sea king) went mega-viral, racking up tens of millions of views. The 2020 TV drama《三十而已》gave it a second viral wave.

海王 emphasizes quantity — juggling many romantic interests at once, like a king ruling over an ocean of fish. It can be used playfully and doesn't necessarily imply malice. 渣男 (zhā nán, 'scum man') emphasizes harm — being emotionally manipulative, cheating, or causing real damage to a partner. A 海王 might be charming and keeping things casual with several people. A 渣男 is actively being a terrible partner. The terms overlap — a 海王 can also be a 渣男 — but 海王 started lighter and more meme-friendly.

Both describe people who spread their attention across many romantic interests, but the intent differs. A 海王 (sea king) is deliberately maintaining multiple relationships — they know what they're doing. A 中央空调 (zhōngyāng kōngtiáo, 'central air conditioning') is someone who's warm and attentive to everyone equally, possibly without romantic intent. The metaphor: central AC cools an entire building without preference. A 中央空调 might just be a genuinely friendly person, while a 海王 is actively playing the field.