The 27-year-old mum, named as Jess Wilkes went overboard and was later found by divers at a depth of six metres, the fire service told AFP.
Five others, including another Briton, were injured in the incident.
The victim, a PA for an architect design firm in London, died on a trip to celebrate her boss’s birthday.
Her devastated family paid tribute to their “larger than life” daughter, who was with her boyfriend at the time of the accident.
Dad Bernard Wilkes, 72, of Lamberhurst, Tunbridge Wells, told The Sun: “What can a father say about losing his only daughter?
"She was a beautiful young girl who lived life to the full. She had a love for life.
“At the moment we’re just in tears. She was beautiful and full of life. She had a seven-year-old daughter."
Grieving friends also posted tributes to the victim (pictured below right) on Facebook.
Her friend Stefanie Menga said: "No word can describe this awful pain in my heart."
Eight friends aged between 20 and 30 -- four French and four British -- were on board the seven metre boat with a pilot aged around 50 when it struck the beacon at 10:45 pm (2045 GMT) on Saturday.
Five were taken to local hospitals after the incident, two with serious injuries. An investigation has been launched to determine the circumstances.
"Everyone is in shock," police said.
"The victims have not been questioned, nor the witnesses."
Local reports state that the small shuttle boat was ferrying passengers between the shore and a large tourist boat when it struck the iron beacon.
An officer with the rescue services said: "There was a metal marker post in the middle of the river to alert boats to watch out for a nearby bridge. The shuttle boat hit this and the woman was catapulted into the water."