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Volunteer manager Jo Guest said there were already about 500 volunteers registered to help at the long-distance Challenge Wanaka triathlon - and the shorter Lake Wanaka Half - both on Saturday.
However, more people were still needed for traffic control on the bike course, around the central race area on Pembroke Park and for ''night shift'' duties on aid stations along the run course.
The latter required people willing to provide support and sustenance to athletes from about 7pm until 11pm.
''For the last few runners that come through, having been going all day, that's where we need the help,'' Miss Guest said.
She encouraged team competitors who would finish their race leg earlier in the day to consider spending some some time volunteering ''if they'd like to give back to the other athletes''.
In the first of the events on the Challenge Wanaka programme, hundreds of competitors took the opportunity to practise on the Roys Bay swim course in fine, calm conditions at dawn yesterday.
Those doing the full challenge on Saturday will complete two laps - a total distance of 3.8km. Competitors are encouraged to do the pre-race swim to acclimatise to open water swimming in a large group and avoid panic attacks on race day.
The lake is considered to be the warmest in the Southern Lakes, however wetsuits are compulsory. During the challenge last year, lake conditions were rough.
Last evening, a 5km charity fun run along the lakefront to Waterfall Creek also attracted a large crowd of entrants of all ages, some dressed in movie star-themed costumes.