Toronto maintains a ferry service in the Toronto harbour to carry passengers to and from Centre Island. Ferries depart every 1/2 hour, starting at 8:00 AM, with the last ferry making its run at 8:30 PM. Tickets are $15 per round trip, and can be purchased as you are boarding the boat. Click here for additional information.
If you miss the ferry, you can always take a water taxi. At a cost of $10 per person, water taxis will take you either to Centre Island, or back to Toronto Harbour. If you require a water taxi, call (416) 203-1773 or (416) 203-TAXI (8294).
While there is currently no public bike system in Toronto, the city is currently exploring this service.