A marine heatwave measuring almost one million square kilometres has been detected off the east coast of New Zealand.
The heatwave has pushed the ocean temperature up by about 5C above the normal temperature of 15C.
The large blob was identified by thermal imaging from the US National Oceanic and Atmospheric Administration.
Victoria University Professor of Physical Geography James Renwick said the heatwave was likely to be caused by warm northerly winds and extended periods of sunshine.
Dr Renwick said, while heatwaves were not unusual, they were happening more often due to the global warming.
He also said marine life was likely to be affected.
Last summer, a marine heatwave around New Zealand waters led to hot, stuffy air temperatures across much of the country, and scientists observed sub-tropical fish swimming far further south.
This time round, it doesn't appear the ocean heat will have much impact on land temperatures, as the currents are moving towards South America.