Pedestrians watched in bemusement as the man swam in the NGV moat.
At first glance, he could have been a participant in a postmodern art instalment.
But Victoria Police failed to see the artistic or the comical when an Irishman, aged in his 40s, wearing board shorts, a snorkel mask and flippers plopped his way across St Kilda Road on Thursday evening.
He then began to snorkel his way around the moat outside the National Gallery of Victoria, much to the bemusement of staff, patrons and onlookers.
Fairfax Radio reported that the man is understood to have "caused trouble outside the gallery" on previous occasions.
Security called for police assistance after the man refused to leave the decorative pool.
Police confirmed on Thursday that an Irish national, aged in his 40s, was arrested for drunk and disorderly behaviour outside the gallery.
Police said the Irishman, aged in his 40s, had been arrested outside the gallery last night for drunk and disorderly behaviour.
A spokeswoman for the NGV said that, for health and safety reasons, it did not condone people entering the moat.