The toddler was found floating in the sea, and attempts to revive her were unsuccessful.
Fijian Police were investigating the incident.
The family, from Great Barrier Island, had arrived at Musket Cove in their 10-metre catamaran Kalamari on Wednesday after sailing from New Zealand.
The Givealittle page said Māhina had been tethered to the boat but “worked free” and ended up in the water.
“By the time we could find her, it was too late,” a friend of the family wrote.
A large number of boaties in the cove, which included doctors and other medical staff, rushed to assist the family.
Musket Cove Resort manager Joe Mar says there is a huge sense of shock across the island.
“The family rushed into shore to seek help and a lot of people rushed to their aid, but unfortunately couldn’t revive her,” he said.
He says the family have now moved inland to Denarau and are being supported by Fiji police.
Island Cruising NZ owner Viki Moore said a number of their participants rushed to the aid of the family.
She said it was common practice when sailing to be tethered to the boat.
“I don’t know what happened in this case, but it is very sad,” Moore said.
“Māhina was a beautiful, happy, smiling child who loved the water and life on the boat,” a family friend wrote.
“Her mother, Kiri, said she had eyes that looked into your soul from the [day] she was born.”
Her parents were now “picking up their lives” and heading back to New Zealand.
“To the beloved Māhina, may you forever live in peace, splashing with joy somewhere in the sea,” the Givealittle page said.
The fundraiser to help with flights and funeral costs has so far raised more than $17000.
A spokeswoman for the Ministry of Foreign Affairs and Trade said it was aware of the death and providing consular assistance to the family.
- additional reporting David Williams
