Mercersburg Area Swim Club, Inc. This is all about us. Welcome to the Mercersburg Area Swim Club's homepage. MASC is a member of three swimming organizations:     1. the Central Pennsylvania Aquatic League (CPAL), which is our winter league,     2. the Interstate Swim League (ISL), which is our summer league, and     3. USA Swimming , an organization that governs age group swimming on a national level. For more information about MASC, contact our League Representative . If you have questions or comments regarding this website, please contact the Web Designer  URL (website address):  http://www.swimmasc.org