At just 10 months old, William and Ellie Trykush are already making a huge splash.

The British twins, from Cirencester, a town in East Gloucestershire, have become worldwide sensations thanks to YouTube clips showing the young pair swimming the full length of a 25-meter pool before they can even walk, or crawl.

"It's the first time I've seen anything like it, where they're blowing water out of their mouths," Amy Stanley, a swimming instructor at their local pool, told ABC News' Lama Hasan.

William and Ellie were born in February to Vic and Charlotte Trykush, herself a former competitive swimmer who swam while she was pregnant with the twins. Charlotte delivered the twins in February, meaning they were born the same year that Olympic fever swept their native country with the London Summer Olympic Games.

"I've seen babies swim underneath before [but] the difference is they can swim on the surface, float and breathe," Charlotte Trykush said of her children's unique talent.

Stanley, the swimming instructor, admits she was equally amazed.

"I went to get all the teachers to come see them," she told Hasan. "It's incredible."

The twins' talent was discovered in October while the family was on vacation and the twins proved able to swim underwater on their own, according to the U.K.'s Daily Mail. When the family returned to their home in Cirencester, the twins continued to swim and learned new techniques, like floating on their backs, the Mail reported.

William and Ellie now swim once a week, usually for about 30 minutes at a time, with their mom and dad and Stanley on hand to guide them, the trio of supervisors told Hasan.

The twins' father says the key to keeping his children comfortable in the water has been for him and his wife to remain calm themselves.

"Avoid teaching of fear," Vic Trykush said, "and teach them not to be scared of the water."