ARRRRRGGH! If it not be Johnny Depp, back as Captain Jack Sparrow to save summer from the choppy waters that was Spider-Man 3. Part three of one of the world's most profitable film franchises arrives with a plot about the fight between pirate freedom and capitalism. And as in all matters of daring-do on the high seas that involve producer Jerry Bruckheimer, there can only be one winner: capitalism. At World's End will surely be as profitable as its predecessor Dead Man's Chest, a film that hauled over a billion dollars in box office treasure despite being broadsided by critics. Some vessels are just unsinkable. Captain Jack Sparrow is worth his weight in gold bullion.

He returns to do battle with the greedy, imperious ways of the East India Trading Company (EITC), led by the Napoleonic Lord Cutler Beckett (Tom Hollander). Beckett has plans to wipe piracy off the sea charts and is forcing Davy Jones (Bill Nighy), the spectral seafarer with octopus tentacles for a beard, to do the dirty work with his indomitable ghost-ship The Flying Dutchman. But first Sparrow has to be rescued from Davy Jones' Locker. "Did no one come to save me just because they missed me?"

he asks. Well, there's that, and then there's the small issue of a billion-dollar franchise.

In Dead Man's Chest, director Gore Verbinski proved you could spend two and half hours at full sail and still be in the cinematic Doldrums. If it wasn't for Depp's slapstick and insouciant bad manners, it would have been entirely lost at sea. It was much too long, the plot was a muddle and it was all middle where it should have had a been beginning and an end.

At World's End is marginally more coherent: it is much too long, the plot is less of a muddle and it seems to have a beginning, a middle and end. But in terms of narrative cinema, that's not really saying much. And it has more salty sub-plots involving doubledealings than you could shake a jolly roger at.

There's Elizabeth Swann (Keira Knightley), the governor's daughter who last time fed Sparrow to a sea monster. But now she needs him back and might be repressing feelings for him too. Captain Hector Barbossa (Geoffrey Rush) is brought back from the dead by black-toothed witch Tia Dalma (Naomie Harris) to lead the rescue expedition to world's end. Barbossa, if you remember, was shot by Sparrow in the first film, so he has unfinished business to settle, while Tia Dalma has her own complicated backstory with Davy Jones that must be resolved.

Then there's Will Turner (Orlando Bloom), the wet fiance of Swann. He plans to shaft Sparrow to free his father Bootstrap Bill Turner (Stellan Skarsgard) from eternal slavery aboard the ghostly Flying Dutchman. And he keeps this secret from his paramour.

They enlist the help of Captain Sap Feng (Chow Yun-Fat), a Singapore pirate who gives them a junk and sea charts leading to Davy Jones' Locker. But he too wants to keelhaul Sparrow as does Lord Cutler Beckett.

It's no wonder Captain Jack Sparrow doesn't show for 40 minutes. And finally there he is, all 43 of him, manning The Black Pearl in multiple variations of himself.

It's an hallucinatory sequence designed especially to give the audience what it really wants . . . as many Johnny Depps as possible.

Would anyone notice if they did away with the rest of the cast altogether?

There is a standard insecurity in Hollywood that package-deal threequels must be bigger, better and longer for fear of losing its audience. So, while last time we had a ship-guzzling monster, At World's End requires you pop at least half a packet of motion sickness tablets to get through it: as part of its overlong final hoard, there's a wedding on the deck of ship in the centre of a swordfight under fire of cannon caught up in a storm to end all storms while swirling on the edge of a giant whirlpool. Whew. It would make the most hardy of seamen uneasy on their legs; somehow, not even Jack Sparrow's eyeliner gets damp.

If the end sequence gives you the feeling of being seduced by a rum-soaked wench, it is hard not to admire a Hollywood film that works so hard at keeping two young lovers apart. It takes Will Turner just over 400 minutes of cinema time to get his lady and by then, he doesn't deserve her, having dashed on the rocks long ago all our affections for him. Keith Richard, who turns up as a pirate who might be Jack Sparrow's dad, provides the film's only surprise: he speaks like a sozzled seadog but he sounds nothing like Jack Sparrow. Then again, as Jerry Bruckheimer will remind you, there's only one Captain Jack Sparrow.