UNICEF's Vanuatu manager hopes improving water systems and sanitation on the island of Erromango will help children develop.
According to the UN agency, 40 percent of children in Vanuatu aged two and a half years old are stunted.
UNICEF with New Zealand's aid programme and the humanitarian agency CARE are trying to clean up the water supply on the island.
The manager Andrew Parker said there is clear relationship between clean water and child development.
"Water supply has a direct bearing, given that stunting is largely influenced, not only by diet, but also by ingestion of faeces," he said.
"So if you don't have clean water, you've got bad sanitation, you've got bad hygiene, you package that together as a negative input to nutrition and intake, you end up with significant stunting."
Andrew Parker said Oceania is the only region globally to see an increase in stunting between 2000 and 2013.