As A Senior (2011-12)
During his senior and final year at St. Bonaventure McMahon showcased his talents among various events … prior to the Atlantic 10 Swimming and Diving Championships McMahon was ranked 20th in the conference in the 200-yard backstroke with a time of 1:57.60 … at the Zippy Invitational he swam his best time of the season in the 50-yard freestyle, coming in at 22.72 … His personal best time in the 50-yard backstroke was seen at the Binghamton meet and at the WNY Invite he swam a 54.72 in the 100-yard butterfly … at the Atlantic 10 Championships he went on to break his previous personal best in the 200-yard backstroke coming in at 1:54.18 … individual top times that were also set at the championships were in the 100-yard backstroke with a time of 52.69, and the 200-yard individual medley where he touched in at 1:68.28. 

As A Junior (2010-11)
At the A-10 Championships, he placed 17th in the 100-yard backstroke with a time of 53.11 and took 16th in the 200-yard backstroke with a time of 1:56.49. 

Before St. Bonaventure
Captain of a two-time Scholastic All-American New Orleans team ... placed in the top 24 of all three of his events at the Sun Belt Conference Championships ... he posted top times in the 200 back (1:52.79) and 1:54.15 in the 200 IM this season ... in high school, McMahon was a Speedo Sectional Qualifier in the 200- and 100-yard backstroke as well as the 100-yard fly and 200-yard IM.