About 600 pupils from schools in Balclutha and throughout Dunedin took part in the march before heading up to Moana Pool for a sausage sizzle and swim.
Police educator Senior Constable Jeanette Parcell said it was the eighth year of the event and the first in which it rained.
It was an attempt to make the pupils feel important for the ''thankless'' task they did in all weather, she said. They were congratulated for their work by Dunedin city councillor Bill Acklin.