A young father who was killed by a four-metre shark while spearfishing off Rottnest has been remembered as a “devoted” dad who was “always in tune with the sea”.

Steven Mattaboni, 38, was in the water with four friends about 1km off Horseshoe Reef when the predator, reportedly a great white, attacked just before 10am on Saturday.

Despite frantic attempts by his mates, who performed CPR on a boat as they raced him to Geordie Bay, and St John ambulance paramedics who were waiting there, he could not be saved.

Mr Mattaboni’s devastated wife, Shirene, said the northern suburbs man was a devoted father of “two beautiful daughters” — one who turns three next month and their four-month-old baby.

“Our hearts are irrevocably broken by the loss of Steven, known affectionately to his mates as ‘Mattas’,” she said.

“An avid fisherman and spearfisherman, who lived and breathed the ocean, he was always in tune with the sea.

“He was fiercely loyal, endlessly generous, and the kind of man who would give you the shirt off his back.

“The world has lost a truly one-of-a-kind gentleman, and our daughters have lost an incredible father far too soon.”

Ms Mattaboni — a specialist nurse — said the family also extended their “deepest, most sincere gratitude” to the emergency services and first responders who worked so tirelessly to save her husband.

“As we try to navigate this incomprehensible loss and grieve the extraordinary man we loved so much, we respectfully ask the media and the public for privacy during this incredibly difficult time,” she said.