About 200 people gathered at Catholic Cathedral College to remember drowning victim Tominiko Junior Pelenato.
Tominiko, 16, drowned on Saturday afternoon while swimming in the lake at the Pegasus Town development in North Canterbury.
Tominiko was lost under water for about 20 minutes as his friends and people nearby desperately tried to bring him to the surface.
Outgoing college principal Bruce Henley, who retired at the end of the term, said the private 200-strong gathering included Tominiko's family, friends, fellow pupils and staff.
"It was very important for that to happen," he said.
"I think they feel as though they are being supported."
Term ended last week and pupils and staff are on holiday.
Pupils were doing "OK" and were being supported by the school, he said.
At least one other person got into difficulty while swimming with Tominiko.
Sergeant Rene Pabst said Tominiko was among five people from a church group to jump into the lake after a game of touch rugby.
The group had been at the lake for an end-of-year breakup, he said. Tominiko and another boy from the group "got into difficulty" in the water.
People from the shore dived in to assist and "they managed to help another boy", but Tominiko could not be found in time.
Bystanders' rescue efforts were hindered by the murkiness of the water, Pabst said.
"Several people jumped in to search for him but it would have been hard to actually spot a person under that water."
Tominiko's swimming ability was one aspect being looked at by police to determine what went wrong, he said, because conditions at the lake were calm that day.
Family and friends were said to be "in a state of shock".
They gathered at the Pelenato household in Linwood yesterday to mourn his loss.
Ngai Tahu placed a rahui (ritual prohibition) on the lake after the incident.
- The Press
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