Around 1,000 guests were gathering to enjoy the view of the Thames pageant as it reaches its end at Tower Bridge.
The guests were given tickets through a ballot offered to residents of the City of London.
Andrew Little, wife Helen, and their children Cameron, seven, and four-year-old Abi came to the bridge from Romford, Essex.
"I work for the City of London Corporation, and we went into a ballot to get tickets," said Mr Little, 38.
"I remember in 1977 my mum taking me to see the Queen for the Silver Jubilee.
Spectators gathered on the banks of the Thames more than seven hours before the boats were due to arrive, with vast crowds expected when the 1,000-strong flotilla of ships and boats sails past later this afternoon.
Umbrellas and waterproof clothing were the essential items on display, along with bunting and Union Flags to wave ahead of the Royal Family's arrival.
Denise and Jim Farrar, from Aldershot, Hampshire, began queuing at 7am before they were allowed through the gates and said the event was a double celebration for them.
Mrs Farrar, 59, said: "We were coronation babies and we've been married 40 years this year so we wanted to come along and celebrate. It's the first time we've ever done anything like this so we wanted to get a good spot."
The Queen and Duke of Edinburgh, along with members of the Royal Family, arrived at Tower Bridge aboard the royal barge, Spirit of Chartwell, at about 4pm.
The royal party then disembarked and took their places aboard HMS President, a former Royal Navy corvette permanently moored near Blackfriars Bridge, to watch the rest of the seven mile-long flotilla.
Up to a million people are expected to line the route of the Thames today to celebrate the Queen's 60 years on the throne.