I'm writing this review because I noticed a lot of people giving it a horrible rating. I can understand why, but I thought I'd give my two cents. This is the underwater movie that makes you think a little bit about what life could be. It might be something that literally changes reality as you know it.
I watched this a lot as a kid, so it's really easy to remember how good it is. The costumes and design are all very nice. So visually you're taken care of pretty well. It falls short on the alien bit. Not even just alien bit but there's a suspenseful creature underwater that's never shown. I thought they did good with not showing it, but I remember my dad absolutely hating that they never showed it when I watched the movie a long time ago. Apparently, towards the end if you check the X-Ray trivia, you'll notice it says they had to reshoot the ending because without it the ending would be too complicated for audiences. So you're in for something a bit more psychological than another alien movie.
In fact, if you're looking for a psychopathic, rampaging, underwater alien killing the crew try Deep Star Six or Leviathan. If you want another movie that's got underwater aliens in it then try The Abyss. Virus is one that takes place on a ship, so you won't get anything underwater, but the psycho alien sort of thing is in that too with the water setting.
I went on a short underwater movie spree awhile ago for some reason, and I always just come back to Sphere cause it does such a good job of making you feel like you're really at the bottom of the ocean and there's this horrifying presence communicating with your crew.
I can see why other people disliked it so much, but since I've seen it probably a dozen times I thought I'd say it's worth it in my opinion.