This is from a video posted around of a middle aged white man sitting in the seat of an airplane during the boarding process. The man wearing a Burger King crown is shown with his face mask pulled below his mouth whilst he yells racial epithets at a woman. The most famous of his quotes is "Kick that N****r bitch off the plane." Which got memed on several right leaning meme sites. I don't know if he faced any repercussions. I just know what this is referencing.
It's a reference for the tendency in horror films involving sharks for the sharks fin to crest the water line. It makes things more tense. If it weren't for them doing that you'd never know they were there. Basically it's saying that that's the only warning you get that this guy is present before something racist is said.
Imagine if you will a black woman boards a plane. She goes to sit down. And all she sees is a burger King crown above the seat line. Now imagine the jaws theme begins slowly ramping up. As the music gets more intense the racist man strikes like in jaws.
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But also what's that got to do with shark fins?