Watch this during the flight and I have to say, it's okay or average. An interesting story which might get interesting but as a two episodes, it can't develop much from the interesting idea.
The story come down to this, you follow a special submarine which which is way advance from what it can be build at that time. Unfortunately, the ship was attack by a similar ship and both got destory in battle and this happen durin WWII. Flash back to present time, something happen during the south pole and you follow the MC to investigate this mysterious phenomena at Antarctica. What you found is this mysterious cylinder and this object will become the main plot of the OVA. The idea is decent to start but like I say, as a two OVA episodes, not much can be done to develop the story. the 1st episode do try to set up the scene of the plot and do well to introduce the MC and people from the show. Unfortunately, the 2nd episodes kinda feel rush a bit as you're moving at a quick pace without knowing the whole sistuation of the plot and the character development. It's disapointment for me as I kinda wish it can develop a bit more than 2 episodes it have and you might have a decent OVA.
For character development, kinda the same thing. You got introduce to the MC and a side character who she is introduce at the beginning. You found out a bit more about them together and how they're connect. Unfortunately, the romance between them feel cheap as like I say, you don't get the feeling between them at all and the only character development between them are two dimensional or cheap to the point where you don't really care what happen to them. Also, the MC and his long lost father feel tack in a bit. It try to do the develoment between them but at the later half of the 2nd episode, it was put aside for the plot development. It did discuss a bit of the MC father and how much he is commmit to the job that he also feel pain not to see his wife one last time. Unfortunately, this all put aside.
Lastly, the two girl, Avatar & Annette, and they difference between what they think about the human was interesting to see but this was kill off too quickly to develop much (even though they do put a flash back at the end to see how much they're interconnect).
If I can put a positive side of this OVA, I guess it will come down to the soundtrack and the action scene. The soundtrack is actually decent to great to listen to. The epic theme song is very cathy and make you pump up a bit when it was use in some scene. For the action scene, it's actually good to watch. To see the big battle between American warship get destroy easily by this alien machine but seeing Atragon atacking the alien warship is great. So, much fun to watch even if they do use some scene quite a few time.
Overall, Super Atragon is really an average OVA. You can see some potential it could have if the story and character development was able to mature a bit more from additional episode, it might be an interesting OVA to watch. Unfortunately, I won't recomend this movie to everyone and might recomend to go watch Blue Submarine NO.6 or Nadia The secret blue water.