A LEISURELY Australia Day float became a harrowing midnight search and rescue mission near Wagga on Sunday night.

Seven people took to the water at Wagga Beach mid-morning with the intention to drift downstream to their campsite at Kohlhagan's Reserve, west of Yarragundry.

It's a river distance which is understood to be more than 25km.

The group - which included four children aged between eight and 15 - were using canoes, small inflatable boats and blow-up thongs to enjoy the day on the water.

But that fun almost turned to tragedy when they became separated and darkness began to fall.

Wagga police duty officer, Inspector Beth Cullen, said the alarm was raised just before midnight that four people were unaccounted.

The call sparked what Inspector Cullen described a "significant" land and water search.

Earlier, one adult and two of the children hopped out of the water in the Ashmont area about 8.30pm, due to the water being too cold.

At that time, the rest of the group were understood to be about half-a-kilometre downstream and the trio were unable to communicate with them.

Police, State Emergency Service (SES) volunteers, members of the Volunteer Rescue Association (VRA) and Ambulance Rescue scoured the area.

The missing four were located on the river bank at a property off Armstrong Road about 2.30am.

"(They) pulled into the bank when it became dangerous after dark and awaited rescue," Inspector Cullen said.

"Fortunately the children were wearing life jackets."

NSW Ambulance Service Riverina duty operations manager Eamonn Purcell said the distance between Roach Road near Ashmont and Kohlhagan's Reserve was about 25km or at least six hours in a kayak.

A command post was established at the reserve, with swift water paramedics jumping on board with the VRA during the search.

Mr Purcell said all involved were assessed by paramedics for minor leg lacerations and slight hypothermia.

It is understood they weren't strong swimmers.

Inspector Cullen said the group had done the right thing by waiting to be rescued but warned those planning to float that they should be aware of how long the trip might take.

Mr Purcell thanked emergency services for again working well together during their second river search in less than two weeks.

Chris Sahn, 19, went missing while swimming upstream of Wagga Beach on January 17; his body recovered three days later after an extensive land, water and air search.