Johnny Depp’s impressive resume is littered with oddballs, from his heartbreaking title role in Edward Scissorhands and iconic B-movie director Ed Wood to a creepily childlike Willy Wonka and the maddest Hatter ever to grace Alice’s Wonderland.

Yet of all these eye-catching roles, he is probably best known as salty seadog Jack Sparrow in the Pirates Of The Caribbean films.

Certainly, it was the first role to earn him a long overdue Oscar nomination as Best Actor.

Orlando Bloom and Keira Knightley may have sailed off into the sunset for the fourth instalment but Depp hoists the mainsail once again as the most fey and quixotic pirate to sail the seven seas, embarking on an action-packed adventure directed by Rob Marshall (Chicago).

Alas, if the third chapter of the series, At World’s End, was a water-logged bore, On Stranger Tides is moored in similar shallows, almost capsizing during an uneventful middle section that should have been edited judiciously to take the running time below two hours.

The introduction of 3D, purely for financial rather than any obvious artistic reasons, doesn’t help the film either, making scenes seem darker, including a night-time attack on the pirates by a school of mermaids that is a whirl of digitally rendered gloom.

This time around, Jack (Depp) joins forces with Barbossa (Geoffrey Rush) to locate the Fountain Of Youth: one of the world’s last undiscovered treasures.

The quest becomes infinitely more perilous when Jack is forced aboard the Queen Anne’s Revenge captained by legendary pirate Blackbeard (Ian McShane), who is also seeking the Fountain, aided by his sexy daughter, Angelica (Penelope Cruz).

Using all of his guile, Jack must somehow outwit Blackbeard and Angelica and reach the Fountain before his rivals.

En route, he crosses paths with rotund King George II (Richard Griffiths) and a hunky priest (Sam Claflin), whose attraction to one of the mermaids (Astrid Berges-Frisbey) tests his faith.

Pirates Of The Caribbean: On Stranger Tides starts off so promisingly with a fast-paced extended sequence in London, which sees Jack escaping from the king’s men by riding on the roofs of moving horse-drawn carriages.

Once the film takes to the water, the plot springs leaks and simmering screen chemistry between Cruz and Depp surprisingly never catches light.

Indeed, there are more sparks between Claflin and his fishy femme – the rising British actor emerges from the flotsam and jetsam with dignity.

McShane is a woefully ineffectual villain while Rush seems to be daydreaming of happier times on The King’s Speech.

Depp is still funny and he delivers the droll one-liners with typical fervour: ‘I support the missionary’s position!’ However, even his considerable talent cannot keep an entire blockbuster afloat and the film runs aground courtesy of Marshall’s plodding direction and a lifeless script.

• Release Date: Wednesday 18 May 2011
• Certificate: 12A
• Runtime: 137mins