The classification of Sea Monsters' subjugation ranks corresponds with the six levels of Sail Battleships; the rough standard is that the length of the Sea Monsters' bodies and the length of the gun decks are matched one-to-one.
Small Species correspond to Level Six and Level 5 Ships (over 30 meters, under 40 meters). Large Species correspond to Fourth-rate Ships and Third Rate Ships (typically 40 meters, 50 meters).
When it comes to enormous Species, nothing short of a Second Grade ship with around one hundred cannons, a First-Class Battleship, or an equivalent Wonder Battleship can contend with them.
Yet, as everyone knows, even the current largest First-Class Battleship in the world, the Sacred Relic and Legendary Warship "Holy Trinity," has a main gun deck length of merely sixty meters.
A creature reaching sixty meters in size is already considered among the elite of the enormous Species of Sea Monsters.
