The Department of Conservation has started its annual survey of the number of humpback whales passing through the Cook Strait.
Observers will spend the next four weeks on Arapawa Island, in the Marlborough Sounds, scanning the sea from dawn to dusk.
They are hoping to catch sight of humpback whales as they travel from Antarctic waters to their South Pacific breeding grounds.
Once spotted, the whales are approached in boats so the researchers can take photographs and skin samples.
DoC says some of the best spotters are former whalers, who can more easily make out the whales in the waves.
Last year, 43 humpback whales were spotted, as well as three minke whales and two sperm whales.