In 2013, police arrested a high school student for taking intrusive pictures of a woman's body from a distance using his smartphone. The 17-year-old had been hiding under a large parasol on a beach in Boryeong, South Chungcheong Province, and took pictures of the woman swimming in the ocean wearing a swimsuit using his phone's zoom feature.
The teen was caught by one of the police officers on patrol at the time. But the victim, an 18-year-old student, had no idea that she had been observed and photographed without her consent.
Among some 940 crimes that have occurred on beaches in the summer over the last three years, sex crimes, including filming or taking pictures of someone's body without their consent, were the third most frequent category, following physical assaults and thefts.
It is also linked to increasing criminal cases that involve using smart devices in South Korea. The number of reported sexual harassment cases using smartphones has increased dramatically since 2009, from about 800 to 4,800 in 2013.
To tackle the issue that has raised serious concerns, the National Police Agency and the Gender Equality Ministry have hired 1,400 public servants and police officers to monitor the public and launch crackdowns on the specific crime on 93 beaches nationwide starting this month.
"Sexual harassment cases using smartphones can happen anywhere, especially in public places including the subway trains," said Choi Su-yeong, deputy director of the women's rights division at Gender Equality Ministry.
"But it's especially common on beaches in the summer because many wear swimsuits in such crowded places."
Not all cases of sexual harassment at summer beaches involve smartphones, according to Choi.
Many of the reported cases involve an offender touching someone's body part without consent in the water, pretending he or she is swimming. A number of people have been arrested for luring tourists to illegal brothels and bars that offer sexual services near the beaches.
Under the current Korean law, taking pictures of another person's body parts which "may cause any sexual stimulus or shame, against the latter's will by using a camera or other similar mechanism" can be punished by imprisonment of a maximum period of five years or a fine up to 10 million won (S$11,738). Those who sell, distribute, lease or openly screen such pictures can also face the same punishment.
Yet the specific crime is difficult to crack down on, mostly because it's a form of voyeurism where the subject of the violation is very often unaware of being harassed, said Choi Jeong-sook, a police officer who currently serves in Busan in charge of monitoring the Haeundae beach.
Many smartphone applications, including those that enable the users to take pictures without a shutter sound, also make it easier for voyeurs to commit their crime.
"The police are doing the best we can to monitor all visitors and find potential offenders," she told The Korea Herald. "But I'm sure (the police crackdown) has its limits. And many cases end up not being reported because victims just don't' know that they have been harassed at all."
The current definition of the particular crime also needs to be more specific, another police officer who wanted to remain anonymous said.
"What does it really mean by 'body parts which may cause any sexual stimulus or shame'? That can be different for everyone," she said. "And it's easy for offenders to get away with the crime by saying, 'I was just taking pictures of the beach and this person just happened to be in it.'"
South Korea is one of the world's most wired countries, with 80 per cent of its population owning smartphones as of last year. The number of smartphone users doubled to 40 million from 2011 to 2014.