MASSIVE jellyfish appear to be "melting" on a Far North beach, as a result of the region's heatwave.

Mission Beach based tour operator Kerryn Bell has photographed about a dozen large true jellyfish in a 500m stretch at Wongaling Beach, appearing as giant puddles in the sand.

The largest, she estimated to be about 60cm wide.

"They came in during the big tides we had, and they've been sitting out in the hot sun, and it looks like they're starting to melt," she said.

"I've never seen that before. It was like looking at melting ice cream."

Ms Bell, who runs Reef Express, reported the odd sighting on Tuesday to the Great Barrier Reef Marine Park Authority via its Eye on the Reef program.

The jellyfish, which are known to gather in large blooms, are not considered as dangerous to humans as box jellyfish or irukandji jellyfish, however they do pack a sting.

Irukandji jellyfish resulted in several beach closures along Cairns' coastline on the weekend, due to large quantities of the potentially deadly marine creatures being collected by surf life savers between Ellis and Holloways beaches.

One swimmer was reported being stung by a jellyfish at Palm Cove on Saturday, and transported themselves to Cairns Hospital for treatment.

Surf Life Saving Queensland Far Northern manager Rob Davidson said Cairns' beaches were likely to remain closed tomorrow, due to the threat of the highly venomous jellyfish.

"We'll continue monitoring the beaches in accordance with our policies, and if there's nothing caught, and the risk goes back to high rather than very high, we will consider reopening the beaches," he said.