Ploessel took over the aquatics programs at Chapman in 1996 when only men’s water polo and women’s swimming were offered. Since then, Ploessel has overseen the additions of women’s water polo as a varsity sport in 1998 and the gradual growth of men’s swimming as a club sport. Both the men’s and women’s water polo teams have improved from winless inaugural seasons to top-10 rankings in Division III under Ploessel and the women’s swimming program continues to grow and sent its first individual ever to the NCAA national championships in 2004. That same year, Ploessel handed over head coaching duties of the Panthers' women's water polo team to his son Eric. Ploessel has also been instrumental in the planning of Chapman's new Olympic-sized Folino Aquatics Facility, which broke ground in August 2006. 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. 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.

With five successful seasons as the head coach of Chapman's women's water polo team under his belt, Eric began his tenure as head men's coach in 2007. It took just one year for Ploessel to guide the Panthers to their first appearance in the WWPA championships in 16 years. On the women's side, the Panthers led the nation in team GPA with a 3.42 mark for the first time ever.

The son of long-time aquatics director Dennis Ploessel, Eric became Chapman's head women's water polo coach in spring 2004 and helped guide the Panthers to their first top-10 national ranking in school history with a 17-13 record. In 2005, Chapman ranked as high as No. 3 in the nation and qualified for the Collegiate III Championhips for the first time ever and finished fourth in the tournament. Ploessel's athletes have also excelled outside of the water as Chapman ranked No. 5 in the nation in team GPA in 2006 with a 3.33 mark.

Prior to becoming head coach of the women, Eric served as men's and women's assistant coach for three seasons. He still serves as an assistant on the men's and women's swimming teams. Eric played collegiately at Long Beach State from 1995-98, scoring 58 career points, including a career-high 20 as a senior. He once notched five goals in an overtime win versus U.C. San Diego.