When you take a standard trip on these generously glasssided and -topped boats, live narrators point out details of interest. The “Red Rover” ticket allows you to hop on and off all day. Boats, which have cafe-bars, depart every 40 min., generally between 9am and 9pm, from four piers: Westminster, London Eye, the Tower, and Greenwich, which covers a lot of the area tourists like seeing. Using it to get to Greenwich can save money off buying several one-way tickets on standard ferries, but simple return tickets are cheaper on the commuters’ Thames Clippers. The 40-min. London Eye River Cruise (www.londoneye.com; [tel] 0870/5000600; £13 adults, £6.50 children 5–16; daily 11:45am–4:45pm) from London Eye pier is less of a value because you can’t get off to explore.