National Geographic photographer Stefano Unterthiner, 48, from Italy has been to more than 30 countries and photographed exotic wildlife such as the Komodo dragon, European bison and brown bear.
When he learnt about Singapore's Bishan otters, he flew here in January last year for over three weeks.
He is not the only foreigner to be intrigued by our otters.
Otter groups here told The New Paper that they get messages from fans across the globe asking where to find the animals if they were to visit Singapore.
There are two species of otters here - the smooth-coated and the small-clawed otters.
The smooth-coated ones grow up to about a metre long and weigh about 11kg. They are the more common ones and have been spotted since the 90s in places such as Sungei Buloh, Bishan-Ang Mo Kio Park and Gardens by the Bay.
Small-clawed otters weigh around 5kg each and have been seen on offshore islands such as Pulau Tekong and Pulau Ubin in recent decades.
Otters have been reported in the media attacking fish ponds in Sentosa Cove or on the tarmac at Changi Airport.
Mr Unterthiner has been a regular contributing photographer for National Geographic Magazine for the past decade. He told TNP in an e-mail interview that he had always dreamt of working with otters.
He said: "My work is telling the life stories of animals, and I am always looking for new and interesting stories... The return of otters in Singapore is an amazing example of co-habitation between people and wildlife.
"It is a positive story to tell and share, full of hope. I never expected to do it in the heart of a metropolis."
Mr Unterthiner went out twice a day, in the early morning and late afternoon, for 21 consecutive days to follow the otters. He mainly photographed the ones in Bishan.
He cycled more than 300km and rarely took a break.
"I was totally exhausted when I finished," he said.
Mr Unterthiner shot about 10,000 images of the otters and saved about 4,500 after editing.
Some of the photos can be seen in the online version of this TNP article and were published in French nature magazine Terre Sauvage on Jan 2.
Mr Unterthiner spent months planning the trip and received help from Ottercity and OtterWatch, a platform that consolidates otter sightings in Singapore since 2009.
VIDEOS YOU SHOULD WATCH
#Joeyjios: We try bubble tea mala hotpot and bubble tea toast
Thirstdays: Where we talk weird dates and wild fantasies
Don't Say Cannot Ep4: He beats people up, but for the country
#Joeyjios: Taste-testing The Alley Luxe and CHICHA San Chen
Office Tea Episode 5: Bosses and Things
#Joeyjios: DIY your way into mum's heart this Mother's Day
Don't Say Cannot Ep3: He 'sees' the world with the help of tech
Office Tea Episode 4: The Dress Code
Caryn Cheng finds the best deals at IMM's Greater Savings Home and Furnishing Sale
#Joeyjios: I try a ballet-inspired workout despite my two left feet