Film Theory: Finding Nemo Doesn't Have A Happy Ending...

This reuniting comes when the fish are then captured in a heavy fishing net, being pulled to the surface. Marlin’s reality is breaking at seeing his son physically once more after moving through the stages of grief that he had conquered, and it’s enough for acceptance to then transform from a healthy realisation, into an acceptance of his own fragmented belief in Nemo’s life: this is the only way he gets to be with him in some form.

There’s something to be said of them being pulled to the surface in the net as if to heaven also, perhaps Marlin travelling out on his own at the end of his depressive stage resulted in his own death, and seeing Nemo again is something of a representation of the two uniting in heaven. They’re surrounded by identical, grey fish - perhaps the slog of souls also on their journey to to the same place. It would explain the incredibly happy ending and the change in Marlin's personality to then allow Nemo out adventuring: they've both made the ultimate sacrifice to now be together.

Far fetched, yes, but they do travel to the land Down Under… maybe one and the same with the underworld where Marlin decides life isn’t worth it if he can’t be with his son. Of course, this then opens a whole new can of worms in why Coral isn't there, and would point to her disappearing after the barracuda attack as something of a choice rather than her own death. Let's leave that for next time, though.