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Family and friends of missing New Zealand Warriors rugby league player Sonny Fai hold out hope he will be found alive after he was swept out to sea from an Auckland beach.

But searchers presume he has drowned after he went into the water with three family members at west Auckland's Bethells Beach on Sunday evening.

His agent Frank Endacott believed 20-year-old Fai had just completed a training run on the beach and had gone to cool off in the surf, Stuff website reported.

It is believed Fai's younger brother became separated from the group and Fai had swum out to help him. He was then struck by a wave and swept away.

The alarm was raised about 8pm (1800 AEDT) on Sunday and two inflatable boats and the Westpac Rescue Helicopter were scrambled to the scene.

Three of the men were rescued, but Fai remained missing when the search was called off, about 10pm.

Fai's sister La Lelei said family members and surf life savers continued the search until 2am on Monday when they were told to go home. They returned three hours later to continue looking.

Players and management from the 40-strong Warriors squad also joined the coastline search from 5am on Monday.

The team had been scheduled for their first training session of the season on Monday morning, and team manager Don Mann said the players were devastated.

It is understood the team has paid for a helicopter to conduct an aerial search, and a police boat and rescue helicopter also continued the search.

Surf Lifeguard patrols had finished for the day, when the alarm was raised with an off-duty lifeguard.

The lifeguard was back on the scene with an inflatable rescue boat within 10 minutes.

All four men found themselves in difficulty, with three being swept in a southerly direction and one in a northerly, said Dean Storey, manager at Surf Life Saving Northern Region.

"Surf lifeguards conducted a search in rough conditions with a 1.5m swell but were unable to locate the man. The Westpac Rescue Helicopter also assisted in the search until low light conditions meant the search was called off at 9.30pm.

"A team of five lifeguards will continue the search of shoreline and coastline until 6pm today (Sunday), and will resume at 10am tomorrow (Monday). We expect to continue the search each morning for the rest of the week," Storey said.

Fai played 15 games for the Warriors, and made his National Rugby League debut in March last year.

He was named Warriors 2007 under-20 player of the year, and was a Junior Kiwis player from 2004-07.

Team management addressed the rest of the team today, when pre-season training officially got under way in Auckland.

Warriors management Don Mann and John Hart went to visit the Fai family this morning.

In a tragic coincidence, it is almost 10 years since the death of another up and coming New Zealand Warriors player.

Tai Savea drowned in the Port Waikato River while on a fishing trip in January 1999. He was also just 20-years-old.