Use this card to send "Poseidra, the Atlantean Dragon" to the Graveyard and add "Legendary Atlantean Tridon" to your hand; Normal Summon "Tridon" and use its effect to Special Summon a "Poseidra" from your hand or Deck, then activate this card's effect to Special Summon the "Poseidra" that was sent to the Graveyard.
If there is this monster or "Deep Sea Diva" on your field, and any other WATER monster in your hand, an OTK can be performed:
Normal Summon this card, then use its effect to send "Atlantean Dragoons" to your Graveyard and add "Atlantean Marksman" to your hand. Activate the effect of "Dragoons" to add "Mermail Abyssmegalo" to your hand. Special Summon "Abyssmegalo" from your hand by discarding "Marksman" and another WATER monster to the Graveyard. Tribute this card, so "Abyssmegalo" can attack twice, and use this card's effect to Special Summon "Marksman". Attack with both, then use the effect of "Marksman" to Special Summon "Atlantean Attack Squad" from your Deck and attack with it.
Normal Summon "Deep Sea Diva" and use its effect to Special Summon this card, then activate its effect to search any "Atlantean" monster. Use both to Synchro Summon "Tatsunoko", and use it with the "Atlantean" monster that was searched, for another Synchro Summon.
Send a Level 3 or lower "Atlantean" monster to your Graveyard to add "Call of the Atlanteans" to your hand. With 1 more low-Leveled Sea Serpent-Type monster in your Graveyard, it can be activated and this card's effect is used again.
Send this card from your Deck to the Graveyard to activate the effect of "Genex Undine", then Special Summon "Atlantean Marksman" from your Graveyard to Xyz Summon a Rank 3 Xyz Monster, or use its effect to Special Summon another "Neptabyss" from your Deck, so its effect can be used from the field.
Use this card as a cost to activate the effect of a Level 7 WATER monster such as "Gungnir, Dragon of the Ice Barrier" or "Mermail Abyssteus", so "Poseidra, the Atlantean Dragon" can be Special Summoned from your Graveyard and use both for a Rank 7 Xyz Summon.
The effect of "Atlantean" monsters in your Deck can be triggered even if this card's effects are negated. Use this to destroy your opponent's cards with "Atlantean Heavy Infantry" and "Atlantean Marksman" after Summoning this card with "Masked Chameleon" or "Bubble Bringer".
Discard this card to activate the effect of "Tidal, Dragon Ruler of Waterfalls" and send any "Atlantean" monster from your Deck to your Graveyard, then Special Summon the sent monster with this card's effect.