In the near future, in response to a series of attacks on ships and ports by an organization known as the USR (Undersea/Underwater Silence Revolution), eleven nations of the world have formed the PKN (Peace Keeping Navy). At the inaugural meeting, the USR commander Admiral Red launches an attack with his advanced submarine, the U-X. When the flagship is in danger of being sunk, the Japanese contribution to the navy, Submarine 707, which arrived late, steers into the path of the torpedoes and is sunk. Six months later, a new 707 and its crew set out to sea to fight Admiral Red.
Tropes
- Artistic License – Ships: None of the submarines of the PKN look very hydrodynamic. Both the original 707 and her namesake successor are the only remotely realistic submarines of the bunch. U-X, on the other hand, is totally hydrodynamic, but the same cannot be said for the other submarines of her fleet.
- Big Bad: Admiral Red. He has an overpowered submarine and an overpowered submarine fleet at his disposal, and seeks to rid the ocean of humanity's "pollution." That aside, not much is known about his motives.
- Cool Boat: Pretty much every single named vessel - and about half the unnamed ones - count for this trope, but the king has to be the Apollo-Norm
, which is so big that what appears to be an Air Force One expy can land on it without any trouble. On top of that, the Apollo can also dive like a submarine, despite it's unfathomable size.note - Curb-Stomp Battle: What the U-X usually delivers, except against the 707.
- Curb Stomp Cushion: Apollo-Norm's fleet is wiped out but the original 707 saves it from getting sunk. That 707's crew SURVIVED is what makes the defeat less tragic!
- Even Evil Has Loved Ones: Admiral Red has a wife and children (three young daughters and one baby boy). The OVA really makes you want him to survive, even if he's a villain.
- Flaunting Your Fleets: The PKN does this at the start, giving Admiral Red a chance to attack the ships and easily sink them as they're too close together to evade his torpedoes.
- Heroic Sacrifice: The original 707 takes the torpedo that Red fired at the super carrier Apollo-Norm. The crew abandoned ship first, so they survived. The captain is still upset about losing his ship.
- Hollywood Tactics: There's plenty of this.
- U-X's sub-to-surface rockets should be impractical to aim, so it's a miracle that they actually hit their targets. A more sound approach would be deploying homing torpedoes from the start.
- For that matter, the destroyers hunting U-X in the beginning should have deployed anti-sub helicopters and used guided torpedoes rather than depth charges, but this can be explained by the fact that U-X used a special torpedo to disable sonar systems, rendering their homing torpedoes useless.
- The PKN's review of its fleet fails to establish an actual chain of command, rendering the whole fleet unable to counter U-X.
- Apollo-Norm and its fleet serving as decoy so that other PKN units can find the USR headquarters. How Admiral Red couldn't see through that ploy is beyond common sense.
- The U-fleet lines up at the edge of the crater in order to sink 707. They're in a position that's easily hit by torpedoes in such a manner that the subs are robbed of their underwater buoyancy.
- Hot Sub-on-Sub Action: U-X dominates and practically destroys everything except for 707.
- Macross Missile Massacre: Lots of it.
- The U-X sinks two American destroyers with these in the beginning of the OVA's first episode.
- When 707 gets trapped in a crater full of unmixed freshwater (where submarines easily sink), a USR fleet does this in hopes of sinking her. Thanks to Captain Hayami's quick thinking to cause a shockwave in order to get out of the crater, 707 dodges the torpedoes and returns the favor by unleashing her spread of torpedoes at the seafloor UNDER the enemy subs. They immediately lose control and buoyancy due to the resulting shockwaves, smashing into each other as they try in vain to get clear of the blast zones.
- Ramming Always Works: 707 rams U-X in the climactic showdown, knocking the latter's main computer offline. Both ships survive, but 707 emerges the victor, having all essential systems intact.
- Red Shirt Army: The PKN's fleets, which are shown getting sunk a lot. That they rely mostly on their advanced tech does NOT help them, as the USR has access to tech even more advanced than the main computer of the American submarine Great Guardian.
- Rock Beats Laser: Almost literally, since even the rebuilt 707 is a conventional diesel-electric submarine (admittedly having a few unconventional accessories aboard but only for support measures) taking on a nuclear-powered super-computer-equipped submarine that easily trashes any PKN fleet. 707 doesn't outright achieve victory more so than simply not getting sunk, which irritates Admiral Red to no end.
- The Captain: Hayami Youhei, a veteran submariner who knows the sea better than anyone in the Japanese Maritime Self-Defense Force.
- Weak, but Skilled: The new 707, despite being brand new, is really not the strongest submarine available as she was built as a conventional diesel-electric with support measures added on (Japan is forbidden from building offensive warships, so the 707 can't carry cruise missiles or long-range torpedoes). Her crew and captain more than compensate for that in combat prowess in unusual waters, allowing the sub to take out a force outnumbering her 17 to 1.
- Worf Effect: The Great Guardian, the most advanced submarine of the US Navy, is shown to be much more powerful than the 707. Using the strategy provided by its powerful tactical supercomputer, she tries to hunt U-X and gets sunk by a barrage of torpedoes.
