By Lincoln Feast

(Reuters) -A barge planned for use building a controversial judging tower for the Paris 2024 Olympic surfing competition in Tahiti snagged on a reef and damaged coral near the contest site on Friday, local opponents said.

Residents of Teahupo'o in October protested plans by Games organisers to build the 14-metre (45-foot) aluminium tower to enable up to 40 people to watch, film and judge the surfing at a famed break in front of the village.

Organisers including Paris 2024 and the French Polynesia government said last month they had decided building a smaller, lighter tower on the site was the best option, allowing for smaller equipment to install it - but still requiring new foundations in the reef.

A video posted on Instagram by Save Teahupo'o Reef, a coalition of locals, surfers and environmental NGOs, showed the barge apparently stuck on the reef, along with broken coral and the barge's damaged propeller.

"The barge got stuck on the reef several times," as locals had predicted, Save Teahupo'o said, adding that this occurred at high tide with no load on the barge.

The group said the authorities had planned to take the opposition associations on the barge on Saturday to show how it would operate but instead went there on Friday without them.

The barge was eventually freed and returned to the marina, the video showed.

'DOES NOT SEEM WORTH IT'

The wave at Teahupo'o is one of surfing's most hallowed venues, where big swells slam onto the shallow tropical reef creating perfect but ferocious tubes.

Teahupo'o has long hosted a contest on the professional world tour, using a modest wooden tower for judges on the reef that locals want to be retained for the Olympics but which organisers say is unsafe.

"This does not feel good and does not seem worth it," Vahine Fierro, a local Tahitian who has qualified for the French Olympic surfing team, commented as she reposted the video.

"I hope that this morning's 'testing' will be enough to prove that we need to adapt to our Polynesian ecosystem norms."

Representatives for Save Teahupo'o did not immediately respond to requests for further comment. Paris 2024 did not immediately respond to a request for comment outside regular business hours.

In a statement to Reuters earlier on Friday, Paris 2024 organisers said they wanted more than ever to continue dialogue with local groups and surfers, having shared numerous documents outlining various studies, options and decisions on the tower.

It said an earlier social media video by protesters showed corals that were not present at the site of the tower's foundations, which would be on a flat, bare part of the reef with "low ecological sensitivity". Some coral outcrops would be carefully moved outside the work zone to protect them, it added.

In California, a small group of protesters gathered on Saturday outside the headquarters of the International Surfing Association, which runs the Olympic surfing events.

"We just don't want to see nature lose again in another battle," protest spokesperson David Anderson told Reuters. "The Olympic committees are sensitive - they don't want bad press - and we feel like this is a fight we can win and we want to raise awareness. We don't want any more drilling into the reef just for an elite judging tower."

The ISA did not immediately respond to requests for comment.

(Reporting by Lincoln Feast in Sydney; Editing by Edwina Gibbs and Christopher Cushing)