Like the Castle Boss, the Submarine Shrine Boss has ridiculously huge LP and two attacks: a triple Fire attack with low damage but a huge range, and a Flake attack (with less range) which can home in on characters and freezes them for 5 seconds upon contact. A good strategy would be to use the Dodge strategy with a Sniper with a Triple Poison 4. Another good way to kill it is by dragging melee characters directly to the boss's head so that it is close enough to it to not get hit by the Flake or Fire attacks, while the ranged characters add more damage to it. Cornering it so that it will not move allows extra damage to be given. The Flake attack's effect can also stack, but since the attack is weak, the characters have a somewhat decent chance of escaping if another character draws the boss' attention. Without the Flake attack, this boss would be very easy. A Freeze Charm 2 will almost always block the freezing effect, which makes melee classes more effective on this boss. A Sniper with a Quint Shot 3 with a Red Stone 3/Freeze Charm 2 combination is an almost infallable way to defeat it, but this is extremely time-consuming due to the Quint Shot's pitiful damage. The Boxer's Poison Knuckle 3 with a Peridot 3 and an ONIGIRI's Card can do significant damage to the boss while dropping Onigiris for the rest of the team, allowing a much bigger chance of surviving. Ice type weapons should also be helpful due to the boss's rather quick firing rate. Thunder type weapons may also be significant, especially when a Topaz is involved.
This is the second mega boss, the first being the Castle Boss.
This is the only boss to have been weakened. Before ver6.7, this boss' Flake attack had an AT of 20-40 with a bigger homing range, while its Fire attack had an AT of 4-6. If this boss was not weakened at all, there is a good chance that it would have been considered much stronger than even the Pyramid Boss.