"Karen Muir was voted into Swimming’s Hall of Fame in 1980. She became the youngest ever world record holder in any sport in 1965, at age 12, when she established a new mark in the 110 yards backstroke. She went on to set 15 world records."
I'm sorry, but this is a GFQ question where the question setter has specifically asked that answers to his questions are not given away on any Q&A site. Please respect his wishes.
If you type the key parts of your questions into a search engine then it comes up with an answer and since that is not a Q&A site then you are abiding by the rules http://duckduckgo.com...t+world+record+holder - assuming the quiz police haven't closed down all search engines yet.
GFQ is Great Fun Quiz from the same organisation that produced GBQ (Great Brain Quiz). GBQ closed because people would not respect the quizsetters wishes about asking on the internet.