Water temperatures in the Australian state of Tasmania have been up to four degrees Celsius hotter than average over the past three months, and scientists have blamed the region's on-going extreme weather on rampant climate change.

Tasmania has already been ravaged by drought, flood and fires this summer, and on Wednesday researchers revealed the state's underwater environments had also been affected by the hotter than normal summer.

Dr Alistair Hobday, from Australia's Commonwealth Science and Industrial Research Organization (CSIRO), said Tasmania's seas had been heating up at an alarming rate since December.

"Tasmanian waters have been incredibly hot," Hobday told the Australian Broadcasting Corporation (ABC) on Wednesday.

"Since satellite records began in the early 1980s we've never seen an event like this."

Despite a collection of such severe weather events having never been recorded in the state before this summer, Hobday said people could expect more of the same in coming years.

"Tasmania's had perhaps a window into the future this summer," Hobday said.

"This summer Tasmania has experienced really dry conditions that led to bushfires in the north of the state."

"Then we had really strong periods of rainfall, massive flooding in parts of Tasmania, and then off our coast this marine heatwave was occurring at the same time -- three really surprising environmental things in Tasmania."

The CSIRO believes the marine heatwave has been caused by a mixture of the East Australian Current bringing warm waters south and Australia's deepening El Nino, which the Australian Bureau of Meteorology has tipped to ease by mid-2016.

Substantial changes in water temperature can cause irreparable damage to marine environments.

Further north in Queensland, Australia's Great Barrier Reef is undergoing its third "bleaching event" in the past 18 years, which has impacted 93 percent of the ecosystem's coral.

Hobday said Tasmania's native marine life faced a similar fate.

"Some animals will be stressed and will die but we'll see new species come into Tasmanian waters," he said.