Ms Dai, 30, considered herself Mr Li's older sister and felt guilty about encouraging him to move to New Zealand in 2012 to study for a masters degree in business administration at the University of Auckland.
She and her husband took him to Uretiti Beach that year, and found it very calm. "So I think it was a mistaken impression for him to see the sea as very safe."
Lifeguards at nearby Ruakaka Beach issued a warning, after Mr Li's death and close calls for several other crabbers, about a temporary sand bar whipped up in the sea by an easterly storm.
She said Mr Li was not a strong swimmer, as his grandparents forbade family members from going in the sea after a relative drowned in China some years ago.
He returned to Uretiti at Christmas with colleagues from a firm he joined as a salesman last month, after graduating from university in November.
Her friend was a "very caring" person who posted a warning on Facebook for others to be careful after four members of two Chinese families died in a collision with a logging truck near Uretiti Beach just two days earlier.
"They were looking for the same beach, I think.
"I don't think Chinese people here are very aware of safety and how to drive safely and how to swim safely."
Mr Li's family and friends - including members of a dog club he had joined with his adopted samoyed Habee - were prepared to raise money to pay for signs.
"If the council needs funding for this, our friends and family can do it."
More than 100 people attended his funeral with family members and his fiancee flying in from China.
Whangarei District Council member Phil Halse welcomed the funding offer, although he said the beach had settled back to its usual calm conditions.
"It's people taking responsibility for themselves - I think it's a great idea." A spokeswoman for the Department of Conservation operator of a popular Uretiti camping ground said it would consider proposals for bilingual signs.
But Auckland Council parks, sports and recreation general manager Ian Maxwell said east coast beaches under his jurisdiction such as Takapuna and Maraetai were not considered dangerous so did not have signs.
"If we were to place signage everywhere for all possible risks, experience suggests they would just become part of the wallpaper and lose any effective impact."
WaterSafe Auckland board member and former chairman Dr Kevin Moran said there was a growing international emphasis on pictorial signs "which speak a thousand words irrespective of your language" and suggested Ms Dai consider helping to relay safety messages through Asian media.
