Pam Gems has taken quite a few liberties with Hans Christian Andersen's famous story and in so doing she has exchanged its stern, even cruel, simplicity (A.S. Byatt has described him as "a psychological terrorist") for more recognisable human complications and a welcome splash of humour.

In Andersen's original, the Little Mermaid falls in love with a prince when she saves him from drowning and, with the help of a sea-witch, exchanges her tail and tongue for legs in the hope that she will find happiness on land with him. If he marries her, she will receive and share his soul, but on the day he marries another, she will be turned to sea-foam, soul-less, and forfeit her mermaid's 300-year lifespan. Mistaking another for his mysterious saviour, the prince marries her instead. The Little Mermaid's sisters sacrifice their long tresses to the sea-witch to pay for a solution: she must, they are told, murder the prince. Silent and good to the last, she refuses, but is swept up by airy female spirits and granted a soul after all.

Gems names the Little Mermaid Undine, after the soul-less sea-sprites of Germanic folklore. As in the original her heroine's bid for freedom and experience seems less admirable than romantically wrong-headed, and her reward for sacrifice and fidelity disappointingly ethereal: erotic love simply slips out of the picture. Lydia Fox as Undine has a dreamy sweetness, however, and manages to convey a good deal in soulful expression when deprived of language.

Undine's father, rather than her sisters, confronts the sea-witch on her behalf. We thus lose female solidarity but gain an intriguing back-story of jealousy and revenge: the king and the witch have history.

It is a shame, especially given the otherwise atmospheric music by Howard Davidson (not to mention the entry about sirens in the programme) that these mermaids do not sing. There isn't much dancing either, although the Little Mermaid is said to excel (in both Andersen and Gems) in using her new feet to advantage, despite enduring the sensation of walking on knives. Flowing trapeze work and acrobatics, especially by Jami Quarrell, are compensation, however, as are the gentle underwater movements of characters in repose, swaying gently like weeds.

Director Sue Parrish and her cast (and their audience of over sevens) clearly enjoyed the quite un-Andersen comic episode, in which horrid Princess Idia (Cassandra Friend) makes an unbridled bid for the prince and ends up with a faceful of choclolates.

Next year is Hans Christian Andersen's bicentenary. If adults now see his tales less as innocent fables than as expressions of a complicated psyche, children will probably enjoy this jollier version of his best-known work.

- Heather Neill (reviewed at the Greenwich Theatre)