A land and marine search is under way in Geraldton after a man believed to have been scuba diving on New Year's Day was reported missing.

The 41-year-old failed to return home on New Year's Day.

Dean Gellatly, 41, was understood to have been diving off St Georges beach yesterday.

When he failed to return home emergency services were notified.

Police, along with volunteer marine rescue crews and SES search teams, are part of a search operation being assisted by a spotter plane and mounted police.

Anyone with information on Mr Gellatly's whereabouts is asked to call police on 131 444.