Under certain conditions, ship waves can have various negative effects. Among them is erosion, and a case in point is Venice, Italy. Passenger transport in the city and lagoon is based mostly on public ship services, managed by Azienda Consorzio Trasporti Veneziano (ACTV). The ACTV fleet consists of 54 water busses or vaporetti, 59 motor crafts, and a few larger units. The waves, pressure fields and propeller slipstreams of public and private transport operating in the main canals - in restricted and often very shallow waters - cause considerable erosion to the many monumental buildings. Reducing wave and propeller wash is thus important for preserving this heritage.