Campers stretch for almost two kilometres from Goftons Beach, swelling the population by up to 5000.

It's New Year's Eve, the busiest night of the year for the seaside town.

At Goftons Beach police park their cars and get ready for their first foot patrol.

There are 16 police on duty, including members of the Road and Public Order Services, formally the Public Order Response Team.

All but three make the walk through the camp ground, stopping to talk to younger groups of campers who are clutching two-litre juice bottles.

"The idea is for the crowd here to see that there's a lot of police on hand - it's a high-visibility policing strategy," said Inspector John Ward, who is in charge of the police operation.

"I just warned that group there that at the moment what they are doing is fine, but if it gets rowdy or gets violent they will be arrested."

It's just after 9pm and not yet dark.

Seasoned police say the trouble won't start until 11pm and will peak again when the last pub closes at 2am.

The first fight breaks out at 9.40pm.

Two teenage boys at the campsite that Inspector Ward warned earlier in the night are held by police, and security guards hold two makeshift weapons - a metal bar and a tyre jack.

A 17-year-old is arrested and put in the back of the divvy van, which has been marked with anatomically confused graffiti during its 30 minutes parked at the beach.

Back at Bridport police station the youth is charged with assault and put out the back to wait for his parents to arrive.

Underage drinking has been the main problem at Bridport and it's hard to prevent in the darkened warren of campsites.

"There's just something about kids and alcohol," Sergeant Ivan Radosavljevick said.

"They just want to fight each other."

A second fight breaks out in the same group of teenagers about 11pm.

Security guards hired by Dorset Council radio police for help and spring back to hold the 30-strong crowd when police arrive.

Car doors slam and two teenagers are on the ground under three police officers apiece, being handcuffed.

Another teenager launches at the sea of high-visibility yellow vests and kicks a police officer to the face.

A girl takes a swing at another police officer.

Two youths already in the back of the van slam their bodies into the walls while their friend gingerly knocks on the wall to let them know he's picked up their hat.

A 16-year-old throws a can of beer at the car and ducks quickly behind his mates.

Another runs at the legs of the police holding his friend, knocking them over and earning himself a place in the van.

Police discuss moving the group on but decide against it: that would just push the problem on to the streets.

Back at the station seven sheepish youths stand against the wall and shuffle one by one into the charge room.

Their parents are called but only two arrive, leaving the others free to slink to the campsite.

The van heads back on the streets for another patrol.

Police are working in teams of three.

Senior Constable Nathaniel Eldershaw says that arrests in a group situation need about five officers each - three to hold the arrestee and two more to watch their backs.

He and Senior Constable Skye Carey drive the van around the streets to an incongruous soundtrack of Rage Against the Machine, stopping to issue formal warnings to people drinking on the street and to move off the road a drowsy man whose celebration peaked too early.

A cheerful young man accepts a $150 fine after being caught drinking on the street for the second time.

"Did you want me to tip my beer out? I'll tip my beer out," he says.

"Hey, did you know you have a penis on the side of your car?"

At 2am the van is parked outside the Bridport Hotel waiting for the pub to close.

A glass lobs from the balcony and hits a police car, the culprit hidden in the crowd.

It's the quietest police have seen the town in years.

Revellers spill out of the hotel and they wish police officers a Happy New Year before trudging home.

The van makes a final loop around the camp sites, where the teenagers who caused trouble earlier huddle in a circle and stare sullenly as it drives past.

Back at the station, Inspector Ward is pleased with how the night went.

Ten youths have been arrested, one for resisting arrest but most for failing to comply with an order to move on.

Sixteen infringement notices for street drinking have been issued, along with 15 youth cautions. Only one person has been arrested for drink-driving.

"You are obviously going to get at least one group that is a problem but you respond in a way that sends a message about what is acceptable and what is not," Inspector Ward said.

"People have a right to celebrate New Year's Eve and have fun, but the families that come here have also got a right to feel safe."

"I'm very happy with the behaviour here tonight. Most people - and that includes most of the teenagers - were happy to do the right thing."