Luke Kay (45) appeared in the Dunedin District Court yesterday, where he pleaded guilty to performing an indecent act on January 21.
He had parked his white Honda Civic in an angled car park at St Clair's Esplanade.
At 12.30am he was noticed by two women in a nearby car to be behaving indecently.
Kay was watching the women while doing so, court documents said.
The women called police, who found the defendant's vehicle still parked.
His pants were still down, with his "genitals exposed", police confirmed.
He gave officers the excuse of airing out his nether regions and was arrested.
Judge Michael Crosbie noted Kay had a previous similar offence from 1994 but no criminal convictions since 2005.
Defence counsel Andrew Dawson highlighted the fact his client had schizophrenia, as part of the wider context to the incident.
"The Esplanade, of course, is a well-known area of town, because of its proximity to the ocean ... That attracts people day and night," the judge said.
"You need to think carefully about the impact your actions and urges have on other people."
Kay was sentenced to 120 hours' community work and nine months' supervision.
Kay's actions were one example of many such reported offences in St Clair and St Kilda in recent years.
