Dion Depace helped rescue people who got into trouble in the water at Christchurch's Scarborough Beach on Friday.

"Natural instinct" kicked in for an Australian tourist when he saw someone yelling for help from a rip at Christchurch's Scarborough Beach.

Dion Depace, 22, rescued one of two people who got into trouble at the beach, in the suburb of Sumner, about 1.30pm on Friday.

The two men were swimming with a group of colleagues when they were caught in the rip about 200 metres right of Cave Rock

GEORGE HEARD/STUFF Three people were taken to Christchurch Hospital, two in a serious condition, after getting caught in a rip at Christchurch's Scarborough Beach on Friday afternoon.

They and their employer, who swallowed water while also assisting in their rescue, were taken to Christchurch Hospital.

READ MORE:

* Police called to a water rescue in Queenstown

* Reporter photographs dramatic water rescue

Depace was in Christchurch on holiday from Melbourne with a group of friends after graduating from university.

GEORGE HEARD/STUFF Australian tourists Brad Moore and Dion Depace saved one of the people who got caught in a rip.

They were swimming at the beach when someone pointed towards a man "just kind of lying" in the water further out and "struggling".

Depace said "natural instinct" kicked in and he swam out to reach the man.

The water was over his head when he reached him.

GEORGE HEARD/STUFF Three people were taken to Christchurch Hospital - two in a serious condition.

"I went out there. I'm pretty tall . . . I couldn't touch the bottom."

He knew it was "not good".

He grabbed the man and started getting him to shallow water. In the meantime "he was pulling me under", he said.

Depace got him to where he could touch the ground, then he let go.

"If I didn't let go I probably would have drowned because I'd inhaled a bit of water."

He asked a friend for help, who carried the man until he could walk on the beach.

GEORGE HEARD/STUFF The Westpac Rescue Helicopter and Coastguard were called to the scene.

"He was adamant he didn't need an ambulance . . . but we made sure [he did].

"It was pretty scary."

James O'Caiside, the employer of the two men caught in the rip, said they were in the water when he arrived and started surfing.

GEORGE HEARD/STUFF Emergency services were called to the beach just after 1.30pm on Friday.

The men were about 50 metres past any other swimmers when O'Caiside heard them calling for help.

He paddled out, got one of them onto his surfboard and headed for shore.

When he thought he was far enough in, O'Caiside stopped to let the man off so he could go back for his other employee.

JOHN KIRK-ANDERSON/STUFF Emergency services responded to reports of a group stuck in a rip near Cave Rock, Scarborough Beach, on Friday. (File photo)

But the man became "panicked" and got pulled back. O'Caiside managed to shout to another swimmer to help him before the Australians arrived and brought him to shore.

"If there hadn't of been three groups of strong swimmers around, they wouldn't have made it back to the beach alive."

After going back into shore to get help for the man still further out, O'Caiside rushed back into the water, drowning his phone in the process.

He thought he was fine but later started vomiting on the beach, and was taken to hospital to recover.

The second man was rescued by Aaron Lock, the owner of Sumner business Learn to Surf.

He spotted the struggling swimmers on a break between lessons, "grabbed" his surfboard and rushed out to the man who was "way out" – about 300 or 400 metres from the shore.

Lock said when he arrived, the man was "pretty scared" but still conscious. He pulled him onto his board and took him to shore where the man seemed to go into a state of shock and was drifting "in and out of consciousness".

"I think we got to him in the nick of time. That's the closest we've come to someone not making it," Lock said.

He warned people of the "dangerous" rip near Cave Rock and said if anyone got caught in it they should attempt to swim across the current. If it was too strong, they should "stay calm, lie on your back and go with it", then wait to swim back.

Sumner Fire Brigade chief Darryl Sayer said three people were taken to hospital – not four as initially reported.

A Canterbury District Health Board spokeswoman said the three people were in a comfortable condition.

After the first rescues, someone reported to Fire and Emergency New Zealand that six more people were caught in the rip, but a Sumner Lifeboat jet ski failed to find them.

A spokeswoman said "it was clear the people had made their own way home".

Surf Life Saving New Zealand southern region manager Stu Bryce said the incident was a reminder for people to swim within their limits.

Volunteer life savers began weekend patrols at popular beaches around Christchurch from November 18.

Daily patrols, sponsored by the Christchurch City Council and Waimakariri District Council, ran from December 18 to January 26.

Scarborough Beach was not patrolled.

"If there's no flags there, definitely look after your mates and enjoy the weather – it's beautiful and the water is warm," Bryce said.

"But look after each other."

WHAT IS A RIP?

A rip current is a strong channel of water flowing away from the shoreline, typically through the surf line, and can happen on any shore that has breaking waves.

Rips look like bands of choppy, darker coloured water. Sometimes you will see foam or debris being carried seawards through a break in the waves.

Myth about rips

Rip currents don't pull people under. People drown because they panic, become exhausted and are not strong enough swimmers to at least tread water.

Escaping from a rip

Don't panic. Float with the current, don't fight it and signal for assistance.

If you are a confident swimmer, swim parallel to the shore until you reach the breaking wave zone, then try to swim back to shore.

If you don't think you can swim parallel to the shore away from the rip, stay calm, float with the rip and signal for help.