"Family and friends saw him swim toward the opposite bank but then lost sight of him," Mr Wright said.
Friends swam across the river shortly after but could not find Mr McIvor.
Whanganui Coast Guard launched its rescue boat and carried out a shoreline and river search, while a helicopter was also used for an aerial sweep of the area. Police staff carried out searches of the river banks on both sides. The search was called off late on Friday but resumed on Saturday when the Police Dive Squad was called in.