The vast majority of international tourist arrivals to New Zealand come through Auckland Airport, which handled nearly fifteen million passengers . Two percent of visitors arrived by sea . Many international tourists spend time in Auckland, Christchurch, Queenstown, Rotorua, and Wellington. Other high-profile destinations include the Bay of Islands, the Waitomo Caves, Aoraki / Mount Cook, and Milford Sound. Many tourists travel considerable distances through the country during their stays, typically using coach lines or hired cars. Though some destinations have seasonal specialities (for winter sports, for example), New Zealand's southern-hemisphere location offers attractions for off-peak northern-hemisphere tourists chasing or avoiding certain seasons. In June 2018 the New Zealand government announced the imposition of a "tourist tax" of around NZ$25 to NZ$35 for international visitors, excluding Australians, many Pacific islanders, and young children. It planned to implement this taxation in 2019 through a newly proposed electronic travel-registration process.