While details are still scarce, La Nuova di Venezia e Mestre reported that the 76-year-old record-holding Italian and two other passengers died when their vessel struck a dam after 9:00 pm on Tuesday, while attempting to establish a new Montecarlo to Venice record.
The other two victims are said to be British racers, whose names remain unknown.
A fourth crewmember, Italian Mario Invernizzi, was transported to a local hospital with serious injuries.
The offshore hull is said to have crashed against the San Nicoletto dam in Lunata, an artificial dam made of large boulders which has been lowered onto the seabed as part of the MOSE project, which seeks to protect the city of Venice and the Venetian Lagoon from flooding.
The powerful boat was about 20 metres long and with engines that allow it to reach speeds of up to 70 knots (about 130 kilometres per hour).
The boat had left Montecarlo on Monday morning at around 11:00 am.
Buzzi was the founder of Italy-based FB Design Group, which specialised in creating high-performance Rigid Hull Inflatable vessels from 10 to 55 feet long.
He began his offshore racing career in 1978, when he won the Italian and European Class 3 Championships.
The following year he set the world speed record for diesel boats using a VM engine at a top speed of 191.58 kilometres per hour.
FB Design boats have won a total of 52 world championships, including the Harmsworth Trophy seven times and have set 40 world speed records.
Buzzi himself won 10 world motorboat racing championships.
When his boat crashed it was near the finish line of the crossing at the Lido di Venezia.