Most were Tamils who feared persecution if they stayed in their homeland.
But this year boat arrivals from Sri Lanka spiked at more than a thousand a month and many are from the majority Sinhalese community - coming in search of jobs and money.
In response, the Australian government has sent hundreds home, most against their will.
Canberra hopes the returns will stem a tide that's overwhelmed Australia's border protection regime.
South Asia Correspondent Michael Edwards begins this report from outside Negombo prison - just 40 kilometres north of Colombo.
A group of alleged people smugglers and their passengers are being held there, after being sent back from Australia.
Correspondent: Michael Edwards
Speakers: Professor G.L. Peiris, Sri Lanka's foreign minister; Jehan Perera, National Peace Council; Sri Lankan asylum seekers
MICHAEL EDWARDS, REPORTER: Their families wait outside the prison. It's a lonely and painful experience.
23-year-old Ranjith Saparamadu has four brothers inside the jail. All have been sent back after paying people smugglers thousands of dollars to get to Australia.
RANJITH SAPARAMADU (voiceover translation): They went there almost one month and they said actually they need a human right or (inaudible) a lawyer or Red Cross. But Australian Immigration said they don't want to give and they say they will give back - they ask them to wait, but they never. My mother and my sister, my niece all are there, but my brothers all they sent back.
MICHAEL EDWARDS: These people represent an emerging trend in asylum seekers coming to Australia. They're from Sri Lanka's majority Singhalese community.
In Singhalese towns and villages the people smugglers' sales pitch is simple: go to Australia and you'll get jobs and money.
Pocus Fernando, a Singhalese fishermen from a small village just north of Negombo, believed the promises.
POCUS FERNANDO (voiceover translation): I wanted to go to Australia for a job to earn money. I have a wife and three daughters to look after. I heard the Australian Government was giving people jobs.
MICHAEL EDWARDS: Pocus is one of dozens in his village to be returned. He's despondent and even more in debt now.
These women were members of Negombo's Singhalese Catholic community. The other thing they have in common is that all their husbands paid smugglers to get to Australia only to be forcibly returned and put in prison.
DAYANI HINDAWITARANA (voiceover translation): My husband is a fisherman. Fishing did not give us sufficient income. We have three children. The Australian Government is known to be generous and to look after people.
MICHAEL EDWARDS: At least 200 men from this community are in prison after being either caught by Sri Lanka's Navy or sent back from Australia. They're facing charges such as leaving the country illegally and in some cases people smuggling. We have been told some of the men have been in prison for six months. Often these families are too poor to get proper legal representation.
SARATH IDDAMALGODA: When the (inaudible) are arrested, they are in custody, families become very poor. Their situation becomes worse. They have to get some more money on loans and they had to prepare these loans. Often they take this - they borrow this money on interest. They have to pay the interest. Their situation becomes worse.
G.L. PEIRIS, SIR LANKAN FOREIGN AFFAIRS MINISTER: People are going in search of greener pastures and they're enticed by various expectations which they are led to entertain by very unscrupulous people who are managing this. The sums involved are very large indeed and the promises that are made are very extravagant.
MICHAEL EDWARDS: At the end of Sri Lanka's brutal civil war in 2009, most asylum seekers were from the minority Tamil community leaving to escape political persecution. Now, they too are coming for economic reasons. They say that while the country is in peace, Tamils don't have the same economic opportunities as Singhalese people.
At a small store outside Negombo Prison is Jude, a Tamil who had arrived back from Australia the day before. For him, Australia represents a chance at a better life.
JUDE (voiceover translation): There's nothing much to do here in Sri Lanka. Therefore I thought of going to Australia to find a job.
MICHAEL EDWARDS: But economics isn't the only imperative. Tamils say they're still leaving for political reasons and that the persecution persists.
Back in Colombo, Krishanan Prytheepan is so fresh off the plane from Australia he says he still hasn't had time to take off the clothes he was given on Christmas Island. He's from Batticaloa in eastern Sri Lanka. He told us that the Sri Lankan Government suspects him of having links with the Tamil Tigers.
KRISHANAN PRYTHEEPAN (voiceover translation): I took the risk of dying in the sea because I know I will die here. But even if I reached Australia and died there, that would be better than dying here in Sri Lanka.
MICHAEL EDWARDS: He tells us he paid people smugglers just under $4,000 and that he could only take with him the clothes he was wearing and that he travelled without a passport.
He says the people smugglers promised him he'd get political asylum and that he'd be given a job. All he got was a small room in the Christmas Island Detention Centre. Krishanan was there for over a month until earlier this week when he was called in for an interview with Immigration officials.
KRISHANAN PRYTHEEPAN (voiceover translation): We were confused and wondered what was going on. We asked, "What's happening to us?" They didn't tell us anything. They told us they were sending us somewhere else. We asked if we were being spent back to Sri Lanka. No-one told us anything. Then one official came up to us. He told us that we might have to go back to Sri Lanka. ... I said to him, "If you're were gonna send us back, kill us instead and sends our bodies."
MICHAEL EDWARDS: Krishanan says the interview lasted less than 20 minutes and at the end of it he was told to pack up his belongings and that he was being sent home. Human rights advocates say this screening process is in breach of international law as the arrivals aren't given adequate opportunities to make a case for asylum.
The Australian Government says any arrivals who have legitimate humanitarian concerns are given refugee status. The chance to escape comes on boats like these. At a Sri Lankan naval base south of Colombo dozens of confiscated fishing boats used by people smugglers sit gently in the water.
I've just been down in the hold of this boat and I almost passed out. It is so hot and so oppressive down there, it's a tiny space, it's about it about four metres by three metres. And I was down there alone. There's no sun today. It's not a particularly hot day. I cannot understand how dozens and dozens of people would fit in such a space and then managed to stay there for 21 days and then come to Australia. It's just unbelievable to think of what lengths these people will go to to get to Australia.
Fishing is a tough way to make a living in Sri Lanka and lately human cargo is proving far more lucrative than fish.
With more than 6,000 Sri Lankans arriving over the past few months, the Australian Government regards this as a big political problem. Australia and Sri Lanka have agreed to boost their naval and intelligence links to combat people smuggling.
An advertising campaign featuring ads on television and in newspapers is also being used to deter potential asylum seekers.
G.L. PEIRIS: I think we have to do a lot more with regard to imparting correct information. Some of the advertisements for example about employment opportunities abroad. People who are not very well informed about these things are duped into investing their hard-earned savings on these very hazardous voyages, unseaworthy vessels and the tragedies of Christmas Island and so on.
MICHAEL EDWARDS: But human rights activists say none of this will work unless the situation in Sri Lanka improves both politically and economically.
JEHAN PERERA, NATIONAL PEACE COUNCIL: Because people want to feel that they are safe and that they are living in a - under civilian authority where there is the rule of law, where there is some place they can go and appeal to. And also where they feel that the economic prospects are brightening for them.
G.L. PEIRIS: The boats have nothing to do with the political situation. The boats have everything to do with the insatiable greed on the part of the people who are organising this.
MICHAEL EDWARDS: Whether they're seeking political asylum or economic opportunities, it seems clear that Sri Lankans will keep taking a chance on the boats and continue to come.