A massive rose-coloured jellyfish, said to resemble a volcano, has washed up on a beach in New Zealand.

Eve and Adam Dickinson and their two children found the lion's mane jellyfish while they were walking on Pakiri Beach, in north Auckland, on Monday.

"[Jellyfish] were everywhere and we were pretty amazed. Then we saw this massive one that seemed different from all of the others," Eve Dickinson said.

"We spent ages looking at it because of its beautiful colours and shape. My boy said it reminded him of a volcano."

National Institute of Water and Atmospheric Research marine biology technician Diana Macpherson said lion's mane jellyfish were "pretty common" in New Zealand during the warmer months.