Okay, a real review
For being your second published work this is pretty good, however, as with your first work, "Syphen Transformation" it suffers from ill-conceived timing. You could have done this movie in roughly half the time by making every shot count. For instance, you could have started off slow just like you did, building tension, but as it got closer and closer you could have just cut back and forth showing the sonar just as it passes the creature on the display rather than making us wait for a full revolution. In the mean-time, some shots of a captain getting more and more nervous, a crew scrambling, the captain stands and order a torpedoe fired, their fear when it misses, etc. With a little work this could really be something. And then once the torpedoe misses the captain orders full-steam away, and to surface, or something like that. But the creature catches them. And then there's the question of why it's after them in the first-place? Maybe this is the first sub designed for the exploration of the deep-deep sea, down where the real monsters live and no sun shines.
Your main problem was timing, your second problem was not developing the story quite enough. However, I do see a couple gems in this work that surprised me and because of that I think you have talent. The way you made the creature dodge the torpedoe was sweet, very anime-esque. And the creature swimming past the window when it was too close for sonar to see, also sweet.
Perhaps a last showdown between the captain and the beast would have been your clincher scene that could have made this movie a true classic. I can just see it, red-emergency lights all over the ship, there's a hull-breach in the aft-section so they close off the doors to prevent the ship scuttling, only we cut away to see the creature make it just past the automatically closing emergency doors. Back to the captain and they start hearing random screams from the aft section, so the crew-members grab weapons and head back there, with the last one being thrown back into the command-center at the last second having been eviscerated. Suddenly the lights go out, and then start flashing like a brown-out, and the last thing the captain sees through the strobe-like light is the creature coming at him illuminated by the flashes of light as he fires his pistol.
I mean, this whole idea could be developed so much more and turned into something really great. So next time don't just take the easy way out and tack on an ending on the credit scene, k? GOOD JOB.