Surfers and beachgoers in Northland are battling an ugly, sticky mess after a large amount of red seaweed washed up on eastern shores.
Now efforts are being made to clean up the sea of rotting red algae on Waipu beach.
In the past, the local councils have let nature take its course, but the seaweed is causing problems for swimmers and surfers, who are getting caught in the smelly mess.
"People don't like swimming in it," says Whangarei District Council waste and drainage manager Andrew Carvell.
"When the tide recedes this stuff coats the shoreline, and in the hot sun it begins to rot. More of it comes in with the tide each cycle, and in the end a thick mat of fresh and decaying matter can build up on the beach."
Mr Carvell says it is hard to manage the seaweed because more washes in with every tide as long as the bloom is happening.
"Such natural processes may cause unpleasant odours, but generally they don't pose a public health risk."
He says no one is completely sure what causes the seaweed invasion at this time of year.
"People have lots of ideas, from the El Niño weather pattern to increasing nutrients in the sea, changing pH, global warming – all sorts of things.
"We don't know exactly why it happens, but we do know that the red algae has been part of the lifecycle of this coast longer than people have."
But while the local councils consider options to manage the seaweed, locals have taken matters into their own hands, using tractors to clear some of the shore.
Watch the video to see the clean-up.