About 12,000 cyclists have taken to the roads around Melbourne, Geelong and Port Phillip Bay for the annual Around the Bay bike ride.

The riders set off on one of six rides, including the 250 kilometre ride which starts in Melbourne, goes around the bay and finishes back in the city, to a 20 kilometre family fun ride.

The event raises money for The Smith Family.

"It's fantastic that riders not only get out there and improve their own fitness but also get out and be charitable and raise money for a great cause," organiser Darren Allen said.

"Even for people who are completely new to cycling they can come and be a part of the event and ride the 20 kilometre event or the 50 kilometre event."

Anton Leschen from The Smith Family said it was their big fundraiser of the year.

"Donations raised by fundraising riders means The Smith Family will be able to support over 2,000 disadvantaged children in their education," he said.

Bikes ferried across at the heads

The race was the biggest single-day cycling event in Australia and this year included a team of 14 pirates who rode Melbourne's rental blue bikes and 16-year-old identical twins who rode unicycles.

"Last year we celebrated our 200,000th rider over the ride's 22-year history," Mr Allen said.

Riders started before dawn for the 250km event. ( ABC News )

"The ride does really attract a whole range of people who do the ride for a bunch of different reasons.

"We have had riders as old as 80 [years old] do the full 210 kilometres and it's great to see kids out there doing the 20 and 50km."

Those who did the longer rides could go either clockwise or counter-clockwise around the bay and Mr Allan said everyone has their favourite route.

"You'd find people would say the toughest way to do this ride is in the clockwise direction and finishing coming up the West Gate Freeway," he said.

When the riders got to Queenscliff or Sorrento they got off their bikes to take the ferry across the heads and Mr Allen said it can get quite busy trying to get up to 650 bikes on a ferry.

"We've made some improvements this year to the process at those sites to help move everyone on a little bit quicker and we've reduced some of the numbers on the ride options so we could get people across quicker," he said.