In the beach everyone wears bikinis. How many women walk in the street with their underwear? None! In the beach it is expected that there will be women in bikinis but in the road it is not expected to see someone's underwear, so in the beach it's considered normal, whereas on the road it's considered slutty, because it's not the norm, it's unexpected and it's out of context. In the beach you wear a bikini to bathe, but there is not reason to walk in the city with your underwear. Do you understand?