The Water Babies, Chichester Festival Theatre, Chichester

The musical film Mary Poppins has hitherto enjoyed pretty much of a monopoly on musical chimney sweeps, with Dick Van Dyke and his colleagues chim-charee, chim-charooing over the roofs of London. Now there's a competitor in the shape of this new musical version of The Water Babies, Charles Kingsley's classic fairy tale from 1863 in which Tom, an oppressed sweep's boy, drowns in the river and re-emerges, squeaky-clean, as one of the eponymous aquatic ecologists whose scout-like job it is to do good.

This show - with a book by Gary Yershon and music and lyrics by Jason Carr - fails to communicate the difficulty and the degradation of Tom's daily labours. We just see him crawling acrobatically around a set of stepladders, which offers little sense of the narrow, maze-like flues of Harthover Hall, where he and his dastardly master Mr Grimes have come to work, and where the sickly-sweet little Ellie is stoically dying of consumption in her dear little room. Despite the dark, dissonant tones in Carr's music, there is not enough here to indicate why Kingsley's book is considered a work of crusading social conscience.

It's in the delightful transformation scene, where both Tom and Grimes drown in a river of billowing silk, that this musical and Jeremy Sams's production burst into witty life. The dust sheets that shroud the set are yanked away. Balloon bubbles float upwards, tethered on strands of weed. A spangled green frog flicks out a party-hooter tongue. Fish - a luscious trout in a figure-hugging rainbow gown and her friend, a sexy black-and-yellow eel - sashay as though on a Parisian catwalk. Meanwhile the gang of water babies (a riot of blue in baseball caps and thigh-length combat trousers) zooms in, elatingly, on micro-scooters.

The show never re-achieves the enchantment of that sequence, though its pleasures were clearly matched, for some of the audience, by the ghoulish scene (which I don't recall from the book) set in an infernal blood-spattered kitchen full of smoking ovens, where sinners cook in their own juices until they've learnt the error of their ways. Human legs roast on spits; hands are chopped off by cleavers; guts are surgically extracted. We seem to have lurched into Sweeney Todd: indeed, acres of the score strike the ear as being sub-Sondheim pastiche.

Neil McDermott brings a tinge of stroppiness to Tom, so that when, as his passport to entering Paradise Gardens, he is enjoined to forgive Grimes (an insufficiently intimidating Joe McGann), you appreciate the moral effort this requires. Elsewhere, in its efforts both to retain the Victorian values of the original and to wink at the present-day punters, the piece veers between throbbing Christian uplift and outrageous camp.

The excellent Louise Gold proves a big asset where unifying the proceedings is concerned. She turns up in a trio of roles: as the mysterious Irishwoman; as the starchy, mark-book-keeping fairy Mrs Bedonebyasyoudid; and as her ludicrously syrupy alter ego, Mrs Doasyouwouldbedoneby, who here swirls on, in a blaze of pink and peroxide, like some Technicolor blonde from a Fifties MGM musical. The latter's simpering song of self-satisfaction at her own global philanthropy ("When a typhoon destroys Tahiti/ I dispense a kiss and a sweetie") is a delicious antidote to little Ellie's soulful warblings which, while they may carry the message of The Water Babies, could never keep it afloat.

To 31 Aug (01243 781312)