Hong Kong has been gripped by political unrest since June 2019, when anti-government protests broke out in the city. District council elections last November saw historic gains made by pro-democracy politicians.
But Hong Kong media outlets - including a pro-Beijing newspaper - have identified some of those on board, while relatives of those detained have also come forward.
The protesters were arrested in the Hong Kong neighborhoods of Yau Mai Tei and Mong Kok.
Shocking footage has captured the moment a 12-year-old girl was violently pushed to the ground and pinned down by riot police in Hong Kong as protests returned to the city over the weekend. Journalists were targeted by police, as were first aiders, secondary school students, and others. Isolated clashes broke out, with protesters throwing umbrellas and water bottles and police responding by firing pepper spray pellets.
When reached by phone, police didn't immediately confirm the arrests. The bus driver subsequently faces charges of driving recklessly, police claiming that he was driving at unsafe speeds, and weapons possession because of the fact that he had a spanner in his possession when apprehended by police. After the arrest, bus drivers have planned a strike in protest.
"The gentleman we arrested this morning was arrested for uttering seditious words under the Crimes Ordinance's section ten", senior superintendent Li Kwai-wah said, referring to legislation enacted in the British colonial era to clamp down anti-government expressions.
In a Facebook statement, police said at least 289 people were arrested, mostly for unlawful assembly.
Some of those identified as being on the speedboat were facing prosecution for involvement in pro-democracy protests previous year.
Did the police take it a step too far with their disciplinary action?
Several well-known activists were arrested during the demonstration including Figo Chan, the vice-convenor of the Civil Human Rights Front and former legislator Leung Kwok-hung, also known as "Long Hair", according to a post on Chan's Facebook page. Al Jazeera's Adrian Brown, reporting from the city, said many people were also carrying out individual acts of defiance across the city, carrying banners or chanting slogans, to protest the new law.
The 12 Hongkongers are aged 16 to 33, and were held on suspicion of "illegal immigration" after they tried to escape by speedboat to the democratic island of Taiwan last month.