The man, who has since been released on bail while investigations continue, reportedly assaulted the woman around 01:00 on Sunday 5 May near the Maritime Museum.
Police said that the alleged victim was in her early 20s and that the pair are believed to know each other.
Pictured: The alleged assault was said to have taken place near the Maritime Museum.
They added that several people were in the area at the time of the reported sexual attack, and would like to speak to anyone who saw it or knows more.
Those with information are urged to contact Police on 612612 or make an anonymous report via the Crimestoppers website.