The fastest and most frequent fleet on the river, with departures from major London piers every 20 minutes. The boats set off from 22 piers across the capital. Discounts with Oyster cards and contactless payment. Download its free in:flow app, which uses GPS tracking to find out your location and provide real-time audio explanation of the sights. River Roamer hop-on-and-off (valid all day from 9am) advance adult £17.80; child £8.90; on the day adult £19.90; child £9.95; under-fives travel free. Adult standard single journeys from £4.90; adult Oyster/app/online single journeys from £4.50.