A sighting of a group of leatherback turtles feeding off Tauranga has sent a ripple of excitement through marine experts and provided the unforgettable climax to an excursion by tourists aboard Bay Explorer.
Sightings were rare of the usually solitary marine reptiles but New Zealand scientific records were turned on their head on Thursday when three were sighted within 100m of each other.
"Three have never been seen together before in New Zealand, it's unprecedented, phenomenal," the owner of Bay Explorer Island and Wildlife Cruises Brandon Stone told Bay of Plenty Times Weekend.
Seeing them feeding and travelling together blew apart the theory that turtles arrived in New Zealand waters haphazardly by accidental drift, he said.
The sightings were captured on video by marine enthusiast Nathan Pettigrew who uses his footage and experiences to give educational talks to schoolchildren.
"To see one in a lifetime is amazing but to see three swimming together was incredible," Mr Pettigrew said.
Turtles the size of tractor tyres were feeding on jellyfish near an off-shore reef when Bay Explorer showed up with passengers from all parts of the world.
The first leatherback spotted was a very large and old turtle with sun damage to its head, quickly followed by two younger turtles. The Bay Explorer last spotted turtles a year ago.
Mr Stone, a 25-year veteran of marine tourism, said the sightings were part of a summer of significant changes observed in marine life entering the Bay.
It included seeing unprecedented numbers of sunfish - the disk-shaped largest true bony fish in the world.
Passengers on Thursday were treated to the sight of sunfish weighing up to 300kg breaching the water and soaring 2m to 3m into the air, including one that splashed passengers when it breached and landed near the bow of the boat.
The most sunfish he had seen in previous years was seven in one day but now he was seeing more than 12 a day every day, feeding on the same jellyfish as the turtles.
Mr Stone was also witnessing a massive increase in blue sharks in open water. Previous summers he had seen a few a week, now it was sometimes 10 to 12 a day.
Common dolphins were also a lot more numerous, with passengers entertained by two to three pods a day gorging on mackerel. He was also seeing more orca and whale sharks and was expecting a great marlin season for big game fishers.
"Tauranga is becoming more and more known for its marine wildlife. People don't understand how much marine life is here."
He was seeing whales on a regular basis, including humpbacks, Bryde's whales and pseudo orca - a bit like a pilot whale.
Niwa's principal fisheries scientist Dr Malcolm Francis said leatherback turtles were usually solitary creatures and, although turtles were not his field of expertise, he had never heard of a group being sighted in New Zealand waters.
They were a bit more tolerant of colder water than other turtles and usually came to public attention when they became tangled in a rope.
Mr Pettigrew appealed for people to be mindful of their plastic bags when it was windy because feeding turtles could mistake them for jellyfish.
Just an hour after Mr Pettigrew was interviewed a Bay of Plenty Times Weekend news team on The Strand waterfront saw the wind whip a plastic bag from a family picnic and deposit it on the sea.
Leatherback turtles (Dermochelys coriacea)
• Most widely distributed of all turtles
• 61 recorded sightings in NZ waters 1892-1996
• Nearest breeding grounds Queensland, Papua New Guinea and Solomon Islands
• Predominant currents in Coral and Tasman seas might carry them to NZ
• Peak sightings in NZ during January and February.
• Historic peaks coincided with raised sea-surface temperatures
- Source: Records of turtles and sea snakes in NZ 1837-1996 by Brian Gill