S4L

S4L means "Shark 4 Life".

The Romanian YouTuber "Highman" calls his community ,,the sharks". Saying you are Shark 4 Life is a way of saying you are a fan of his and part of his community.

"Cristian: I am S4L!
Daniel: What does this mean?
Cristian: I am a shark for life, a fan of Highman!
Daniel: Oh, cool!"