Their main monster, "Deep Sea Diva", Special Summons a Level 3 or lower Sea Serpent monster from the Deck, which includes all of this series' members. The new Main Deck monsters from Eternity Code have effects that activate by sending the top cards from their controller's Deck to the GY when they are Special Summoned. They interact with Level 4 or lower WATER monsters in the GY by Special Summoning them with "Artisan", adding them to the hand with "Sentry", or placing them on the top or bottom of the Deck with "Minstrel". The series Synchro Monster, "Deep Sea Prima Donna", makes use of the opponent's banished cards to take Level 4 or lower WATER monsters from the Deck and either Special Summon them or add them to the hand.
While these monsters can't overwhelm the opponent on their own, they can be used along with other WATER monsters to further extend their combos and gain access to powerful Extra Deck monsters. The "Atlantean" monsters have effects that activate when they are sent to the GY to activate the effect of another WATER monster. Since the "Deep Sea" monsters activate their effects by sending the top cards from the Deck to the GY, they can possibly trigger the effects of the "Atlanteans" without having to search them first. In addition, "Neptabyss, the Atlantean Prince" can be used with "Atlantean Dragoons" to add any Sea Serpent monster from the Deck to the hand, which greatly improve this series' consistency.
- There have been small amount of WATER monsters that were released before "Deep Sea Diva" in Raging Battle that share the same kanji as this series (
深 海Shinkai) in their Japanese names, most of whom have "Deepsea" (without spacing) in their English names, but are not related to this series. Those cards include "Abyssal Kingshark", "Deepsea Macrotrema", "Deepsea Shark", "Deepsea Warrior", "Superancient Deepsea King Coelacanth", "The Dragon Dwelling in the Deep", and "Rage of the Deep Sea".