Some 789 people at a music festival in eastern Finland went skinny dipping on Saturday, organisers said, beating the previous record set in Australia by just three, reports said.
Organisers were waiting for Guinness World Records to confirm the record.
It is the third Finnish attempt at the record, Yle news website said.
Previous attempts in Helsinki in 2015 and 2016 each attracted about 300 participants.
Organisers at the Ilosaari Rock music festival in Joensuu had hoped to entice 1,000 people into the chilly water.
As in previous attempts, only a few hundred volunteers appeared to be willing to participate, but shortly before the event was due to begin the sun came out and this boosted the numbers, Yle reported.
The record they were hoping to break was achieved in 2015 in Perth by 786 people at an attempt to celebrate positive body image.
Outdoor swimming is a tradition in Finland, where "avantouinti" - ice-hole swimming - is promoted by the country's tourist board as an energy-boosting experience.
Hundreds of naked swimmers have taken to the water in Finland in a bid to break the world record for the biggest naked swim.