Curious onlookers gathered on bridges as dozens of boats snaked along the River Seine on Monday, in a rehearsal for the Paris Olympics’ unique opening ceremony next month.

A total of 55 boats made the journey from Pont d'Austerlitz, named after a French military victory in 1805, to Pont d'Iena, a stone's throw from the Eiffel Tower, the nation's most striking and best-known landmark.

Officials are confident that the nearly four-hour ceremony will run like clockwork on July 26.

"Six months ago, we had like a 10 minutes delay on the timing, and today we are very close, almost to the second, to our targets," Thierry Reboul, the executive director for ceremonies said. "So it is very satisfying. We've respected an extremely precise level of timing."

On the day of the eagerly-awaited event, around 200 Olympic delegations will join the parade on more than 80 boats. They will make the journey from east to west, along a six-kilometer route which has become a major talking point, both for its audacity as a unique open-air event and for its exposure to potential danger.

Security concerns led French President Emmanuel Macron to say in mid-April that the ceremony could shift to Stade de France if the threat level was too high. But Reboul said Monday that authorities are setting up for the big day as originally planned, with no alternatives being prepared at this stage.

There will be a final rehearsal, involving the full armada of boats, before the opening ceremony, which is expected to bring 100 world leaders to the city's embankments, where more than 300,000 people will watch.

"We will give our heart and souls to make it a great success for the French people," France's Sports Minister Amelie Oudea-Castera said Monday. "They deserve it."

The rehearsal saw 10 police speedboats shadowing the convoy, as well as speedboats equipped with television cameras. There were armed police officers stationed at various points along the way. The boats crossed 16 bridges, passing by iconic landmarks such as the green-tinged Grand Palais, where the fencing and taekwondo events will be held.