Eschewing the Labour leader's plans to reduce class sizes for five-, six- and seven-year-olds, another candidate promised instead to buy all schools a swimming pool.
"They're desperate people, these Conservatives," said Mr Blair, standing four-square with the candidates. "You will see in this election that they will try to scare and frighten people about me and the Labour Party. But it's they who are cracking up."
Despite Tory protestations and his antics aboard the 72ft barge, Mr Blair had not gone potty. And neither had the other candidates, Alex Doona and Rory Lowings, both aged six.
They were accompanying Mr Blair and his wife, Cherie, aboard The Redshank, sailing back and forth along a section of Bristol Docks to highlight Labour's commitment to reducing class sizes.
Alex and Rory are standing as candidates in elections at Oldbury Court primary school. Like Mr Blair, they are standing on 1 May; unlike him, they can make wild promises to the electorate.
Rory, who is standing for the Star Wars Party, said: "If I was Prime Minister, I'd give money to every school in the world to buy a swimming pool."
Then, unprompted by any Labour spin doctors, he added: "I'd vote for Tony Blair. He'd make a good Prime Minister."
Alex called for "more maths and fewer stories", adding: "If I were Prime Minister, I'd make the school carpets a bit softer."
But it wasn't all serious stuff. When asked why the Labour leader was in a barge, a party press officer replied: "The children are doing a project on transport, so the message is that Labour is committed to improving our transport networks."
Barges? "Well, under the Conservatives, Britain's inland waterways have been completely neglected. They could take a lot of freight and passengers. We will make sure that the waterways are used for the benefit of the public."Reuse content