Swimming Wellington operations manager Henrietta Latham says the Junior Metro League aims to increase participation in the sport by providing a team environment for achievement.
"It is an initiative which will continue to develop the swimmers, with an emphasis on fun and team involvement.
"It will be high tempo and exciting. As all swimmers are part of a team, points are only awarded to teams."
Events consist of sprints and relays in four age groups.
The 9-years and under swimmers will race in one group, while the 10-years and under have the option of competing with their peers or "swimming up" a grade.
Each session will end with an eight-person team "splash and dash" relay, featuring a boy and girl from each age group swimming a 25m lap.
"The 200m canon relay will be the only relay in any of our competitions where junior swimmers of all ages and abilities can compete in the same race," said Latham.
"We expect a lot of close finishes."
Wanganui Swimming Club head coach Andy McLay, whose Aquablasts team is hosting today, said his young team was looking forward to competing against swimmers in other regions.
"It's not often we get to travel to Wellington three times to compete in such a short space of time.
"The competition will be good for the development of our young swimmers."
The Wanganui club will be holding their end-of-season prize-giving on Sunday, beginning at 2.30pm at the Kaierau Country Club.
