Ploessel took over the aquatics programs at Chapman in 1996 when it offered just men's water polo and women's swimming. Since then, Ploessel has overseen the additions of women's water polo as a varsity sport in 1998 and the expansion into diving with the completion of the Allred Olympic Pool in 2008, and in 2012-13 the transition of men's swimming and diving from club sport to varsity Division III.
Chapman's women's swimming program continues to improve with school records falling every winter and spring. In 2012, Ploessel's third swimmer qualified for the Division III National Championships when Julie Case became the first swimmer in school history to medal at the PCSC Championships and be named Division III Swimmer of the Meet. Case added her name to the list of Ploessel's accomplishments when she earned Chapman's first-ever individual SCIAC Championship, taking first in the 1,650 meter freestyle race in the 2013 conference championships.
In 2014, Ploessel had two divers qualify for the Division III National Championships for the first time in school history, while female diver Kayla Dimicco became the first Chapman diver to receive All-SCIAC honors and the second swimming and diving athlete to earn All-SCIAC for the Panthers.
Ploessel's student-athletes have thrived as Chapman's men's and women's water polo teams consistently rank among the top academic teams in the country, and in 2006, Chapman's women's team compiled a GPA of 3.33 and ranked fifth in the country - ahead of school's such as Princeton, U.C. San Diego and USC. The men faired almost as well in 2005, ranking 10th in the nation with a team GPA of 3.07. The Panthers' women's swimming and diving team has also won CSCAA Academic honors every semester since Fall 2010.
Prior to joining the Chapman coaching ranks, Ploessel coached water polo and swimming at Cypress College and at Los Alamitos High School, where he continues to teach full time as a resource specialist. He swam and played collegiate water polo at Cal State Fullerton from 1968-73 while earning his bachelor's degree in physical education. He received a master's degree in special education from Cal Lutheran in 1979.