The DC movie Aquaman (《海王》) hit Chinese cinemas on December 7, 2018, and grossed over $290 million domestically. The slang meaning emerged a few months later, building on an older meme: actor Zhang Han's line in a drama with Zhao Liying — '承包你的鱼塘' (I'll contract your fish pond) — had already made 鱼塘 (fish pond) slang for someone's roster of romantic interests. In March 2019, the phrase '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 on Douyin, racking up tens of millions of views by May.

The meme spawned an entire vocabulary: a Sea King's collection of romantic interests is a 鱼塘, maintaining multiple flirtations is 养鱼 (raising fish), and a related synonym 中央空调 (central air conditioning) describes someone who gives warmth to everyone equally. In 2020, the TV drama 《三十而已》 (Nothing But Thirty) gave the term a second viral wave when audiences called the cheating character Liang Zhengxian a 海王 — at this point the term shifted from playful teasing toward something closer to 渣男 (scum man), implying real disloyalty.

Now standard vocabulary across all major platforms. Mostly aimed at men but increasingly gender-neutral — Xiaohongshu users apply it to women too. The term is used both as an accusation and as ironic self-deprecation: someone might caption a photo with three friends as '海王出巡' (the Sea King on patrol). Sociolinguistic studies note it's primarily used by post-90s and post-00s generations, almost always in spoken or informal written Chinese.