Students dressed as Charlie Chaplin, Superman and a genie were among about 60 people arrested in Christchurch as students celebrated the end of lectures for the year.
Canterbury University's annual Tea Party and Lincoln University's Garden Party kicked off yesterday morning and continued into the night.
By 8.30pm 63 people had been arrested, mostly for breaching the liquor ban. Several people were also being held by police for "detoxification" because they were so drunk.
Sergeant Richard Ryan said most people had been "pretty understanding" of the arrests.
"The majority of people have been pretty good about it and haven't kicked up a fuss," he said. "We're really trying to nip the drinking in the bud so that it doesn't get worse throughout the night. A lot of these people have been drinking all day and we don't want it to escalate."
Most of those arrested would be given a pre-charge warning and would not have to appear in court, Ryan said.
"We will take them in and process them for a few hours until they sober up and then they will not be charged."
University of Canterbury Students' Association (UCSA) president Erin Jackson said there had been a "relaxed and positive" atmosphere at the Tea Party.
"Everyone is in a really good mood. The local cops have been through and were very happy with how it's going."
However, she said it was disappointing to hear 60 people had been arrested.
"I think it's important to distinguish between that and people being arrested for disorderly behaviour. We did our best to tell people before the event to take note of the liquor ban and obey it.
"We think the problem was this morning before the event; a lot of people go from flat to flat and that's where this has occurred," she said.
"It is disappointing to hear students have been arrested but there have been no problems at the actual event."
Police had been in contact with the UCSA during the planning stages of the R18 event and were happy with the measures it put in place.
The Tea Party event finished about 5.30pm, but after parties were expected to continue into the evening. The Lincoln Garden Party finished at 4.30pm and hundreds of students had boarded 15 buses to come into Christchurch.
Police would be out in force in the area until about 3am, to "crack down" on liquor ban breaches, Ryan said.
A Selwyn police spokesman said most of the district's police staff monitored the Lincoln event. With student drinking games such as "eight [drinks] before eight [am]", police were expecting minor disorder later in the day.
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