What exactly is the plot?

I've got three different takes here:

"SS as Chris Cody drags his team of mercenaries to S America to find and destroy a renegage scientist who`s developed a mind altering drug." from one of the posters in a different thread.

"Chris Kody, the world's best mercenary, is freed from prison -- but there's a catch. Kody must use his lethal weapons and fighting skills to stop a group of terrorists who have taken over a nuclear sub." from the plot outline on IMDb.

"At 20,000 fathoms the only creature more dangerous than a biological mutant is...man." from the tagline.

What is this movie about???? It looks like a complete mess in trying to decide whether it's a rip-off of "Leviathan", a jungle adventure or another "Die Hard/Under Siege" type movie set in a submarine.

From the comments in this group I don't seem any the wiser, and that the film-makers were writing the script as they were going along.