Seesaw is funded by advertising - viewers see unskippable 60-second ad breaks before and during each show. Advertisers including Ikea, Diageo and Kraft have already signed up.
Seesaw was born from technology bought by Arquiva from the aborted Project Kangaroo, an internet TV service supported by several UK broadcasters that was blocked by the Competition Commission.
Seesaw's chief executive, John Keeling, has said that the site would roll out a premium service in the next few months, which would involve customers making micropayments to view or "rent" major shows.
While the service will initially be purely a streaming outlet, there are plans to add social networking elements to the Seesaw site, said head of product and technology Richard Dines, who previously worked on Project Kangaroo.
Both Mr Dines and Mr Keeling were reluctant to make comparisons between the two initiatives. "It's a different story," said Mr Keeling. "Lessons were learned by the shareholders of Kangaroo. We have a different model - we don't have broadcasters as shareholders."
However he credited the catch-up services developed individually by the major broadcasters - such as 4OD, the BBC iPlayer and Demand Five - for opening up a market for internet TV.
"You need a big player to change the way people watch television," he said.
But with broadcasters already pointing viewers to their own services, the challenge for SeeSaw and similar companies such as Blinkbox is to divert enough users away, said Chris Curtis, news editor at industry publication Broadcast.
"The difficulty for all these guys is getting enough viewers to site to view the content to make the advertising model stack up," he said.
"It's quite hard to get people to pay for content online. They might be prepared to make micropayments for the really big American shows but people generally associate conventional, standard TV with being free at point of viewing."
