The traditional Neretva River boat marathon is held under the auspices of President Ivo Josipovic, who inaugurated the race from a command boat. He was joined by Parliament Speaker Josip Leko.
The 12-member boat crews will row from Metkovic down the Neretva to the seaport of Ploce, a course long 22.6 km.
Before the start, President Josipovic said this was a "wonderful event which combines tradition, tourism, sport and hospitality."
Speaking to the press, he said he always felt good at this boat marathon, describing it as one of the best tourism and cultural events.
Leko said the marathon was proof of perseverance and unity.
"Just as the winner of this marathon needs the solidarity of everyone and the principle 'one for all, all for one', because it's the only way to win, so we in Croatia have to align our activity and we will overcome the difficulties we are in," he said, adding that "we solve problems through unity, hard work and commitment."
Tens of thousands of visitors are watching the race.
The winners will be presented with an award by President Josipovic in Ploce tonight.