The rooftop at the Standard Hotel opens at 2PM on Sundays and it gets pretty crowded relatively quickly. So if you're not dressed to the nines and you don't "know a guy" it's best to get there early and settle in on one of the pink couches with a pitcher of mojito.
With a great view of Manhattan on one side and Jersey on the other it's important to take a second to peel your eyes from the beautiful people basking in the sunlight if only for a moment. Then by all means go back to ogling, you're wearing sunglasses no one can tell.
As the drinks start flowing and the music gets louder, the ambiance shifts from a relaxing Sunday afternoon on a patio to a more festive occasion. I didn't see it with my own eyes, but I'm told that skinny dipping is a regular event. Maybe next time I'll have the courage to start that off.