The Busan Coast Guard said on Friday that it had taken the suspect into custody on suspicion of violating the Act on Special Cases Concerning the Punishment of Sexual Crimes.
Authorities also booked an Uzbekistan national in their 20s without detention on the same charges.
The Uzbek national allegedly made physical contact with three other female beachgoers, also on Sunday.
Investigators said the two suspects did not act in concert, but independently targeted women who were swimming.
Neither of them were under the influence of alcohol at the time of the alleged offenses. Drug tests for both came back negative.
Police have implemented protective measures for the victims and plan to refer the case to prosecutors after completing the investigation.
A Coast Guard official said the agency “will respond sternly to sex crimes targeting beachgoers this summer, regardless of nationality.”
Translated from the JoongAng Ilbo using generative AI and edited by Korea JoongAng Daily staff.