Meaning:
“海” means “ocean,” and “王” means “king.” In Greek mythology, the “king of the ocean” is Poseidon. In comics, he is Aquaman. However, Chinese netizens have come up with a different meaning for this term, based on a metaphor that compares womanizing to fishing. “King of the ocean” refers to a womanizer who is involved in several affairs at the same time and is constantly chasing new women.
Example:
A: 上周约你看电影的男生人怎么样？
Shàngzhōu yuē nǐ kàn diànyǐng de nánshēng rén zěnmeyàng？
How’s the guy who asked you out on a movie date?
B: 我们一起去看电影，结果遇到另一个女生，质问他怎么背着自己约别人，我非常尴尬。
Wǒmen yīqǐ qù kàn diànyǐng，jiéguǒ yùdào lìngyīge nǚshēng，zhìwèn tā zěnme bèi zhe zìjǐ yuē biérén，wǒ fēicháng gāngà。
We went to see a movie, but ran into his other girlfriend who challenged him as to why he was on a date with someone else. I was so embarrassed.
A: 原来他是海王。幸好被你及早发现了。
Yuánlái tā shì hǎiwáng。Xìnghǎo bèi nǐ jízǎo fāxiàn le。
So he’s a womanizer. Luckily you found out the truth about him early.