As Sunday's Standard Chartered Singapore Marathon was under way, several unusual guests joined in - a group of 16 otters.
Ten adult otters and six babies were seen at around 7.25am at a section of the marathon route that cut through Gardens by the Bay.
According to otter enthusiasts, the animals had slept in Gardens by the Bay overnight.
The adults were up at around 6am and out looking for food, before returning at 7.25am to collect the babies to forage together.
Almost an hour later, the otters moved to another part of Gardens by the Bay and were spotted rolling around on the ground to dry themselves, to the delight of event participants who whipped out their mobile phones to snap photos.
Mr Bernard Seah, 49, a wildlife photographer and Otter Working Group volunteer, was at Gardens by the Bay with four others to help facilitate the movement of the otters across the busy race route.
The Otter Working Group is made up of representatives from the public and various government and other agencies involved in the welfare of otters.
Mr Seah said he and other enthusiasts alerted the group on Thursday to contact the race organiser as there was a chance that the otters would be at the Gardens by the Bay section of the marathon route.
"If the runners are doing their thing and the otters try to cross their path, the otters might be afraid and not know why the humans are running towards them," said Mr Seah.
"The adult otters might be protective of their babies, and there might have been a possibility of human-otter conflict."
The Otter Working Group got in touch with the marathon organiser on Friday and both parties discussed scenarios that could unfold if the otters came close to or stayed overnight at the marathon route.
Mr Seah said race officials told him they would inform their volunteers along the route to keep a lookout for otters and guide them away from harm if necessary. They would also check the area before the run. A day before the race, "our worst fears came true as (the otters) were actually sleeping just a few metres from the race route", he said.
On Sunday, five people - two from the Otter Working Group and three volunteers from the otter-watching community - went to the marathon route in Gardens by the Bay to inform runners about the otters' presence in the area, as well as to step in if necessary.
But all was peaceful on the day and the otters were able to make their way around Gardens by the Bay, delighting those who encountered them.