'Long and painful road to recovery': Woman celebrating 30th among four friends badly hurt in Sydney boat explosion

A Sydney woman who was celebrating her 30th birthday is among the six people injured, four seriously, when a boat exploded on the Hawkesbury River over Easter.

Mirka Tothova, who is originally from Slovakia, has been left in a critical condition with burns to 30 per cent of her body, after the Easter Sunday accident on the Hawkesbury River, according to a fundraising page.

She is being treated at the Royal North Shore Hospital in Sydney, the page said, after the accident which happened during a party with her friends and partner, Joe Kwon.

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He described Ms Tothova as "a beautiful and energetic young woman who came to Australia from Slovakia to start a new life".

"Mirka was admitted to the Royal North Shore hospital in a critical state with deep burns to 30 per cent of her body: mainly her hands, arms, legs and front torso," the page said.

"Mirka is currently in the intensive burns unit undergoing skin grafting surgery and multiple other painful treatments.

"Roughly every three days she needs to have her wounds cleaned to remove the dead tissue so she does not get an infection.

"This is an extremely painful process which causes extreme fever after every procedure.

"There is no timeframe as to when Mirka will be discharged from hospital, but we have been told by the doctors that it will be a long and painful road to recovery."

Ms Tothova, who runs a Sydney health food store, was one of four friends who were seriously injured when the boat exploded while being refuelled at Brooklyn on Easter Sunday.

Childcare worker, Ale Osr, who is from Mexico but living in Gladesville on a student visa, was also badly hurt according to another fundraising website.

"She suffered severe burns to about 60 per cent of her body. She is currently in ICU at RNSH where she faces a long and painful road to recovery," it said.

Karolina Santana, from Brazil, who runs a beauty business is also being treated for "severe burns".

A donation page set up for her said her partner, Sam, was also hurt.

It described Ms Santana as a "beautiful, sweet and caring person, who is loved by everyone she comes across."

"The accident has led to severe burns to over 30 per cent of Karoline's body and will require ongoing hospitalisation and multiple medical procedures," it said.

"Her partner Sam has got five per cent burns to his body and has been bedside by Karoline in the Royal North Shore hospital as her parents are currently in Brazil and have no immediate family members in Australia."

NSW Ambulance Inspector David Morris earlier said the incident as the worst he's seen in 15 years and described the scene as chaotic.

A postman was among those who rushed to help after the blast.

Firefighters were involved in driving ambulances in order to free up paramedics to work on the patients as they were raced to hospital.

NSW Police provided escorts for the ambulances to help them through the heavy Easter weekend traffic.

The blaze was extinguished but the boat was destroyed and sunk in shallow waters.

The cause of the fire is being investigated.