The city club won seven medals, including three golds.
Olympian Anthony James (pictured) may have missed out on the World Championships in Kazan, but he proved a class above the rest to claim the men’s 100m butterfly title in an impressive time of 52.20 seconds, which ranks him in the world’s top 25.
Youngster Sam Dailley destroyed his rivals in the same event for 13/14 year-olds. Dailley won by more than two seconds, clocking 56.48. He also picked up a bronze medal in the boys’ 14/16 4x100m relay.
The team event was were Plymouth Leander’s other gold on the first day came. It was achieved by their women’s 4x100m relay squad of Juliette Casini, Eliza Duffy, Shauna Lee and Melanie Houghton.
Belgium champion Casini also won a bronze in the 17/18 women’s 200m freestyle with a time of 2:01.18.
There were also third place finishes for Great Britain international Laura Stephens in the 16-year-olds 50m butterfly (28.06) and Tegan Drew in the 15-year-olds version (28.51).
The competition in South Yorkshire lasts until Sunday.