This is the risk you run by looking cool and sitting on the rail. You know what's not cool? Losing your balance! You know what's even less cool than losing your balance? Getting super wet when you don't want to. You know what's ultimately not cool? I think you know where I'm going with this - losing your balance and falling into water, getting wet when you don't want to. Wow, this guy really ticked all the boxes for not being cool.
I hope his friends are ready to jump in and save him after he's smacked his head against the wall and fallen into the water. This picture catches them in that phase where they haven't fully realized that something has gone wrong yet. That's what makes a great photo like this. You need seemingly uncaring people to look at the person while they fail.