How warm is the sea for swimming in?

Because of the various currents which feed the near shore waters of New Zealand, sea temperatures vary considerably depending on where you are. The warmest areas are the Northland, Bay of Plenty and the north East Cape on the North Island where temperatures range from around 20 degrees Celsius at their warmest (February) to 15 degrees Celsius at their coldest (September). Generally then the further south you go the colder the water gets with the Dunedin and south of the South Island ranging from 8 to 13 degrees Celsius. The exception to this is the Christchurch/Banks Peninsular areas on the South Island which have ocean temperatures similar to much of the East Cape and the Taranaki region on the North Island.

Oceans and lake temperatures will be completely dependant on their depth and how they are fed and expect most rivers to be chilly.

Outside of summer you will need a wetsuit unless you are feeling brave.