I wouldn't recommend watching the Theatrical Cut of The Abyss. It's a decent film but the ending is so butchered that it has you wondering what the hell happened. It just doesn't make any sense.

However, the ending to the Special Edition isn't perfect either. It clears things up, it tells you why there are these florescent aliens swimming about, but in the extended edition they're less likable - in the original cut Bud (Ed Harris) disarms a nuclear warhead, is saved by aliens and then meets them for about two seconds before being taken back to the surface; it's nonsensical but at least the aliens seem helpful and friendly. In the Special Edition, though, you see that these aliens are on the brink of destroying the world. They can control the waves so they're going to flood everything. And when Bud asks why they're going to do this, they show lots of shots of nuclear bombs going off on some watery video screen. Here they seem a bit preachy and just a little bit psychotic. But then inspired by Bud's love for his wife, they change their mind and the waves dissipate. The aquatic nutballs realise that we're not all bad and that there's no need for watery genocide. Suddenly they're a bunch of extraterrestrial hippies.

But although the message of the Special Edition is pap in the extreme (war is bad, okay? Why can't we all just get along?), it's at least an acceptable resolution. You're not left scratching your head.

But the aliens are perhaps one of the least satisfactory aspects of the film. In parts the film becomes Close Encounters underwater, yet the wide-eyed wonder is just a little bit cornier than it should be. Much more successful is the Cold War paranoia and the working class banter amongst the characters. Cameron is no Spielberg.

For me, the most enjoyable parts of the film are those dealing with Coffey (Michael Biehn). He's a Navy Seal who has to hitch a ride on Bud's underwater drilling platform to locate a sunken nuclear sub. At the beginning his mission is just to look for survivors, but when the aliens show up he thinks they're Russians. Cue psychosis.

The progression from normality to lunacy isn't exactly handled with subtlety (Coffey goes mad almost instantly; a reaction to being so deep underwater), but it's fun. One of my favourite bits is when the divers are talking and Coffey is discretely cutting his arm under the table. Mental just doesn't describe him adequately. And I also like it when the divers confront him after he brings a nuclear warhead onto the rig. He says something about them doing an 'about-face', but Biehn delivers the line superbly; he hisses it like a snake. And then once they leave, you see that he's been holding a gun behind his back all the time. Again he's just completely lost the plot. But what makes him such a good character is that he doesn't think he's mad. He thinks what he's doing is for everyone's good; he thinks there are commies down there. So as dangerous and crazy as he is, he ends up being something of a pathetic figure. Indeed, even his death isn't cause for celebration. After an excellent submarine chase he falls down into the abyss and dies when the sub cracks under the pressure. Soldier boy just couldn't take the strain.

But although Coffey is the most fun character (if fun is the correct word), Ed Harris is the person who makes the film work. You can feed him the corniest lines and he'll somehow make them seem genuine. And he'll give them a ring of truth because he's so damn intense. Just take the resuscitation scene. It's silly in the extreme. Bud's wife drowns after the chase with Coffey and Bud then takes her back to the rig. He then resuscitates her. It really shouldn't work, and we've seen so many resuscitation scenes that they're clichéd beyond belief, but Harris jumps into the scene with such vigour that it ends up being one of the best scenes in the film. He gives CPR like a madman and yells "Fight!" at the top of his lungs before slapping his wife across the face. It's pretty hardcore. And then when his wife wakes up (after an interminable length of time), a shaking of the head, which would be the normal reaction, is replaced by a goofy grin.

And credit also has to go to Mary Elizabeth Mastrantonio as Bud's wife Lindsey. She gives an excellent performance and she joins Ripley and Sarah Connor as female characters that are genuinely tough. These days there are tons of annoying lipstick heroines that are supposed to be 'empowered' – women who can fire over-sized guns and 'kick ass'. But they're usually anorexic models with balloon tits; they're about as tough as a glass of water. But Cameron has a habit of creating genuinely tough female characters, ones that feel like the real deal.

However, as good as Harris, Biehn and Mastrantonio are, the rest of the cast are far from stellar. In fact, some of the acting is downright dire. But it's weird, although there's some cringeworthy "Oh my god!" moments, and although there's some unconvincing crying and some bad line delivery, there's genuine chemistry between the actors which makes up for some of the shortcomings when it comes to craft.

But to be fair, the bad acting isn't limited to the supporting cast. Mastrantonio suffers in the scene where she has to talk to Bud as he's journeying down the abyss to disarm the nuke. But then again, the script doesn't help her much. She has to talk some nonsense about candles. However, that's Cameron for you. He's a master at action but an amateur at emotions. Just watch Titanic for another lesson.