Although recruited as a backstroker/freestyler Dennen unexpectedly made his first Senior National qualifying time in the 400 individual medley, smashing the cut by two seconds with a time of 4:32.22. Up until that swim, his plan focused on making the 200 meter backstroke National qualifying time because he always saw himself as a backstroke/freestyler. Not only did he make the qualifying cut in the 400 IM, but he also accomplished his goal in the 200 meter backstroke a few days later with a time of 2:07.10. These two performances met his high school career goal of being able to head to Yale with several Senior National qualifying times.

During his career at Atlantic City High School Dennen received the MVP award for four years, and he broke five school records. At the New Jersey State Championships he placed second in the 200 freestyle with a respectable 1:42.00, and third in the 100 backstroke. Prior to those swims Dennen made his first Junior National cuts in the 1500 and 500 yard freestyles and 200 backstroke. His repertoire during high school reflects his versatility and depth as a swimmer.

Dennen chose Yale because of the camaraderie of the men's team and the potential of the new Bulldog Class of 2009 and the prospect of future classes. Dennen's home team, the Atlantic City Aquatic Club, was quite small, never even big enough for a relay. So while he plans to continue to improve and contribute big points against the other Ivy League teams, he also hopes to gain a berth on at least one relay.

Living at the NJ beach, Dennen enjoys surfing and wakeboarding.