The world sailing federation voiced disappointment on Tuesday after a dolphin show was held at an Olympic test event near Tokyo, sparking criticism.
The dolphin display was part of opening ceremonies for the World Cup series on Enoshima island on Sunday, which hundreds of athletes and officials attended.
The event drew criticism, including from British yachtsman Luke Patience, who won a silver medal at the London 2012 games.
"Couldn't be more embarrassed with what I'm witnessing. We are sailors, and apparently a 'green' sport," he wrote on Twitter, with a photo apparently depicting the dolphin show.
He later tweeted: "I was shocked when World Sailing took us to a dolphin aquarium for an opening ceremony. As a sport, I hope we can show more morality than this."
World Sailing, the sport's governing body, said in a statement it was "disappointed" that the opening events included a dolphin display, which animal rights activists say is cruel exploitation.
"World Sailing does not condone displays of this nature and apologises for the misjudgement and any offence caused."
They said that all ceremony-related content must be pre-approved, but "no such approval was given nor sought" from the organising committee for the show.
"As part of World Sailing's Sustainability Agenda 2030, there are specific targets linked to marine life," said the statement.
"One of which is to mitigate negative impacts sailing can have on marine cetaceans by 2020 by producing guidance, as necessary, which will be provided to our event partners to ensure this does not happen again."
Japan's sailing federation also offered an apology, according to local media.
"If there were people who were offended, I'd like to apologise," said the federation head Hirobumi Kawano.
"We should have recognised this as a sensitive issue. We were not careful," said Kawano, who added that different countries and individuals have different views on the treatment of dolphins.
The news came a day after officials said there had been major progress in preparations at Enoshima for Tokyo 2020.
A World Sailing official said that they had "really seen a big change" since April when the federation criticised Tokyo 2020 for being behind schedule.
The federation said they will gather feedback from the sailors and race officials at the Enoshima regatta to get ready for Tokyo 2020.