The acting was questionable, the premise of underwater monsters was strange, and the back story generic, but for a mindless action flick, it wasn't bad. How exactly would YOU make a movie about giant robots up to your standards? Do tell.
Well, the first thing I would do, would be to have them fight with their gun/ranged weapons before they even got near a monster, instead of wading in like a metal Chuck Norris.
Or how about that big ass sword? I don't remember the movie perfectly, but once they were battling and were almost destroyed and THEN at the last moment, they remembered the big ass sword.
I don't know about tank divisions in the US Army (was communications), but I'm pretty sure they don't go on a bumper tank spree and only use their cannon when they remember it.
These two things alone ruined the movie for someone that can usually suspend a lot of disbelief.