Yes, this looks like a postcard, but I took this photo on a warm spring afternoon when my 4:30 conference call cancelled. Carpe diem!
If you live in SF, Baker Beach is an option on a sunny day. If you are visiting SF, don't expect a Caribbean-type beach, but the Golden Gate Bridge view is nice! (as you walk closer to the bridge, there is a nude beach area).
Lesson: if your 4:30 conference call cancels, go outside & enjoy something beautiful for an hour!