Three family members have suffered burns in an explosion aboard their boat on the NSW Central Coast.
The 35-year-old man, 34-year-old woman and their two sons, eight and seven, had just left the wharf when the blast occurred.
The woman, who suffered serious burns to her arms, legs and torso jumped into the water with the eight-year-old, who was burned on his legs.
The man received burns to his arms and legs.
A passing boatie helped get them back to shore before paramedics arrived.
The woman was airlifted to Westmead Hospital in a serious condition while the man and two children were taken by road.
The seven-year-old escaped injury but was treated for shock.
Officers from the NSW Police Marine Area Command have been tasked with determining the cause of the explosion.