HOW often would anyone see a platypus swimming up the Hobart Rivulet? Not very often, it’s safe to say.

But workers at the Royal Hobart Hospital redevelopment spotted this little monotreme frolicking in the close quarters of the rivulet on Collins St yesterday.

A John Holland Fairbrother Joint Venture spokesman said it was an unusual sighting near the redevelopment.

“Onlookers were fascinated to watch this little fellow outside our construction offices in the Hobart Rivulet, going about its business in water,” he said.