The prospect of a sequel to Finding Nemo may make most fans sound exactly like that picture's resident worrywart, Marlin: Do we really need a sequel some 13 years later? But Finding Nemo is perfect: why risk ruining it?

The new film’s box-office performance - $782,613,925 to date, with territories yet to conquer - suggests that Pixar has called it right. And it has, we think. If you stick around for the post-credits sequence, you’ll discover what happened to Willem Dafoe’s Tank Gang after the 2003 adventure. But by then, the viewer will have made new screen friends, including Ed O’Neill’s opportunistic octopus, Kaitlin Olson’s cheerful shark-whale and Idris Elba’s cranky seal.

Finding Nemo sent an overprotective dad off in search of his missing and only son; Finding Dory reverses the central quest by sending Dory, Marlin's much-loved, memory-challenged sidekick, off in search of her parents.

The quest brings Marlin, Dory and Nemo to a Marine Life Institute in California - where Sigourney Weaver narrates the attractions, while fishier folk get into scrapes and monkeyshines.

Chase scenes ensue, but these shenanigans are tempered by Dory's flashbacks to childhood, wherein her doting, warm parents Charlie (Eugene Levy) and Jenny (Diane Keaton) rise to special challenges of parenting a disabled child. You probably won't need as many tissues as you did for Inside Out last year, but you will need them.

As before, Ellen DeGeneres and Albert Brooks make for charming mismatched buddies although, wisely, the screenplay contrives to separate them, thereby ensuring that Finding Dory has its own texture, tone and journey. It's a given from Pixar, but the animation is superb; its aquarium-coloured tableaux are almost as involving as the adventure.

There are commendable lessons here about being resilient and resourceful and kind, but you’ll have fun learning them.