It looks like the sunny South-east is taking a moment to bask in whatever light contemporary art might throw off. Following the opening of Turner Contemporary in nearby Margate, another battered English seaside town opens a major art exhibition. Following a well-received debut in 2008, the Folkestone Triennial, curated by Andrea Schlieker, sees 19 international artists occupying the town with artworks. It's immigration and globalisation, issues that come to bear particularly on Folkestone because of its position on the Channel, which appear to have been the guiding themes here. A shuttered beach café houses a film following immigrants trying to enter Britain by Nikolaj Bendix Skyum Larsen, while Hala Elkoussy's collection of artefacts relating to Cairo's colonial history occupies a high street shopfront. Hew Locke's collection of model ships strung with gold booty hang prettily from the eaves of a church, gesturing to histories of plundering sea trade and migration.
Much of the most engaging work here strays off message, however. On the Leas overlooking the sea is Spencer Finch's wheel of 100 Pantone colour reference chips fixed to a viewing frame through which one looks out at the watery horizon, spinning the wheel until one finds an appropriate match for the tint of the sea. Of course, none of these flat, even tones can match the fluid, changeable qualities of light and colour on water – neither Pantones 621 nor 7026 can do justice to the pale, nacreous aquamarine of an optimistic Folkestone morning. It's the attempt, however, that reminds you of this.
At 12 o'clock each day someone takes a reading from the wheel, chooses the appropriate shade and raises a correspondingly dyed flag on to a set of flagpoles on Sandgate Road. Well you might call it 12 o'clock, or you might call it 5: Ruth Ewan has positioned several clocks around Folkestone that tell French Revolutionary time, the confusing, decimal system that was introduced, unsuccessfully, in France in 1793 following the formation of the French Republic. The title of Ewan's work – We Could Have Been Anything That We Wanted to Be – is a reminder of the contingency of structural systems such as timekeeping, but also of an inability to escape the systems that we've inherited, given that time is essentially an act of co-operation on an unthinkably grand scale.
A K Dolven has rescued a bell from a Leicester church that was scrapped for not being in tune with the others. Now hung, lonely and isolated from two poles over a bleak expanse of tarmac, it can be run once more. Dolven replaced the bell's clapper – it was as though its tongue had been cut out – and, like the Little Mermaid, gave it back its voice. Actually, that only happened in the 1989 Disney film version. In Hans Christian Andersen's dark, melancholic story, written in 1836, the mermaid throws herself, tongueless, into the sea. A bleak tale, yes, but a popular one – her statue in Copenhagen is a major tourist attraction, a fact that takes us tripping down to Folkestone's Sunny Sands beach, where Cornelia Parker's The Folkestone Mermaid, a new bronze sculpture, sits on the rocks gazing out to sea. Based on a cast of a local woman, she cuts a tougher, more no-nonsense figure than her suicidal Copenhagen twin. Folkestone is pragmatic, then, but optimistic.
To 25 September (www.folkestonetriennial.org.uk)