Dillon learned to swim at the age of three when his mom taught him to float on his back in the deep end of their local YMCA pool, in Hazleton, PA. By age seven he followed in his brothers' footsteps and began swimming competitively. Like their father, the three Abeysinghe brothers were born swimmers. For five years, they were members of the Dayton Raiders Swim Club in Ohio, before the family returned to their father’s native Sri Lanka. There, in the city of Colombo, the family founded their own aquatics club, as Dillon and his two brothers led the team to more than 10 national championships, and earned national school colors in the process. All three brothers were members of the Sri Lankan national team for over five years and represented their country at multiple international competitions. Outside the pool, Dillon is an avid surfer, cyclist, and painter and also owns a dog-walking business with his brother Kyle.