Almost all harbour cruises leave from Wharf 6, Circular Quay and some from Darling Harbour. However, apart from the running commentary, most offer nothing that you won't get on a regular harbour ferry for a lot less: the best of the ordinary trips is to Manly. The Australian Travel Specialists at Jetty 2 and 6, Circular Quay, the Harbourside Shopping Centre at Darling Harbour, and Manly Wharf (tel 9247 5151), book all cruises.

If you really want to splash out, you could take a water taxi ride - Circular Quay to Watsons Bay, for example, costs $45 for the first passenger and then an additional $6 for each extra person. Pick-ups with Taxis Afloat are available from any wharf if booked in advance on tel 9955 3222. One water taxi company, Watertour, located on Cockle Bay wharf in Darling Harbour (tel 9267 0099, www.watertours ), now also offers tours on bright yellow taxis looking like New York cabs on the water, from $10 for a half-hour spin.

Sydney Harbour Ferry Cruises - run by State Transit - seem to offer the best value: choose between the Morning River Cruise (daily 10am & 11.15am; 1hr; $14), the recommended Afternoon Harbour Cruise to Middle Harbour and back (Mon-Fri 1pm, Sat & Sun 1.30pm; 2hr 30min; $21), or the Evening Cruise (Mon-Sat 8pm; 1hr 30min; $18).

Captain Cook Cruises at Jetty 6 (tel 9206 1111, www.captaincook.com.au ) is the big commercial operator, with huge-capacity boats offering a variety of cruises. All involve lunch, dinner or morning/afternoon tea; a lunch cruise will set you back $52. They also have a hop-on, hop-off Sydney Harbour Explorer (9.30am-5.30pm; $22) circuiting between Circular Quay, the Opera House, Watsons Bay, Taronga Zoo and Darling Harbour.

Matilda Cruises , based at the Aquarium Wharf, Darling Harbour (tel 9264 7377, www.matilda.com.au ), offer various smaller-scale cruises on sailing catamarans (engines mostly used), with big foredecks providing great views; all depart from Darling Harbour but pick up later from Circular Quay. Cruises range from two-hour Coffee or Luncheon Cruises ($26-53.50), to a four-course Dinner Cruise ($103). Their hop-on hop-off one-hour Rocket Harbour Express Cruise commences from Darling Harbour, stopping at the Opera House, Circular Quay, Taronga Zoo and Watsons Bay (every 30min 9.30am-4.30pm; $19.50), while their Rocket Express service shuttles between Darling Harbour, the casino and Circular Quay ($4).

There are also several more romantic sailing trips to consider. The Bounty (office at 29 George St, The Rocks; tel 9247 1789, www.bounty.com ), offers various outings from Campbells Cove - most involving food and entertainment - on a replica of Captain Bligh's ship made for the film starring Mel Gibson; Sunday brunch is cheapest (10-11.30am; $53). With Sydney by Sail (tel 9280 1110, www.sydneybysail.com ) there are shorter yacht sails on Port Jackson (1hr 30min; $54) and longer ones going further into surrounding inlets (3hr; $98). Departures, from Darling Harbour's National Maritime Museum, include admission to the museum. Sail Svanen (tel 9698 4456, www.sailsvanen.com ), moored at Campbells Cove, offer luncheon sails on the harbour for $83.50, or longer overnight trips to Broken Bay ($275).

To get the adrenaline pumping, options include the amphibious Aussie Duck (tel 13 1007, www.aussieduck.com ), a fifty-seater "coach" which after a 45-minute city tour makes a startling "splash-down" into the harbour and transforms into a jet-powered boat (1hr 45min; $49.50). Ocean Extreme (mobile tel 0414/800 046, www.oceanextreme.com.au ) offer an "Adrenaline Tour" on a rigid inflatable boat at speeds of more than 100km/hour (40min; $60).