I can't remember the name!

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I saw a movie some time ago with my husband and liked it alot. I was trying to think of the name of it and I just can't. It is way old. The color is that super bright stuff. It is about two submarines, one is the good guys and the other is the bad guys. The good guys find a "lost" city in a bubble. While there, they see lots of gold and diamonds. One tries to take some diamonds back with him. When he gets to the surface and opens his duffle, they are dust. The bad guys have an island too. There are really huge vicious animals under the control of the chief bad dude. The good and bad clash and the good prevail. Has anyone seen this movie? Do you know what it is called?