Nine-month-old twins William and Ellenita Trykush cannot walk, crawl or even sit up – but swimming a full lap at their local 25m pool, unaided, is no problem.
The twin boys, from Gloucestershire in England's southwest, have amazed their swim instructors by the way they can float on their backs and let their kick propel them from one end of the pool to the other.
They do it wearing only a swim nappy – and without arm bands or floats.
"I thought all babies could do it," mother Charley Trykush told the BBC.
"It wasn't until we were here and all the swimming teachers were so excited about it that we realised how unusual it was and how clever they are."
Amy Stanley, an instructor at the pool in Cirencester, said the boys' parents were "very relaxed" in the water and did not panic whenever they are submerged during "rotating" exercises.
"When they're not quite coming around quick enough, mum and dad don't panic – they just let them come around in their own time," she said.
Source: BBC News.