The man was holding a small axe and demanded the victim's keys and wallet, which the victim handed over.
The man punched the victim on the head and face, and then tried to steal the car, only to crashed it into another parked car.
The man then attacked his victim with the axe and knocked him unconscious. During the assault the victim's friend heard the commotion and came to his aid.
He was assaulted by both the offender and a second man, who was seen earlier with the first offender at the wharf.
He was punched in the head and face and fell into a bush area, Mr Shewry said.
The attackers left in their own vehicle, which was described as a 5-door, dark-coloured people mover, possibly a station wagon.
The second victim then realised his friend was missing and searched for him for some time, eventually finding him injured and laying on rocks some distance away, he said.
"This was a nasty, unprovoked attack on two men who were simply enjoying a night out fishing.
"The first victim received serious facial injuries, including a fractured cheek and jaw, as well as a head wound and cuts to his hands and his upper legs. He is likely to require ongoing specialist treatment for the damage to his face."
The second victim had cuts and bruises to his facial area and a possible fractured hand, Mr Shewry said.
The man who had been fishing by himself was believed to have chatted to the two offenders, but left before the incident happened. Police would like to speak to this man as soon as possible.
The first offender was described as Maori or Pacific Islander, about 1.75m tall, aged between 25 and 35. He wore a hooded sweatshirt and three-quarter length pants.
The second offender was described as Maori or Pacific Islander, about 1.78-1.8m tall, aged in his late 30s.
The lone fisherman was described as a tall Maori or Pacific Islander of skinny build. He was driving a white-coloured older model station wagon, which had a rear tail light that wasn't working.
He also had a large dog with him, Mr Shewry said.
"We have a number of inquiries underway and have conducted a forensic scene examination at the wharf."
Anyone with information was asked to contact Mr Shewry on 021 191 4085 or 09 420 9732, or anonymously to Crimestoppers on 0800 555 111.