The Darkfin series is a series of DARK monsters comprised of Fish, Aqua, and Sea Serpent-Type monsters. These monsters all carry a slightly twisted appearance, but not all of them are vicious-looking creatures. Also, all of them have dark coloring on their bodies, usually around the fins, flippers, etc., keeping with the namesake. The gameplay with Darkfins involves constant use of face-down Attack Position, like a predator in wait.
Most Darkfin monsters have average ATK, but some have higher ATK, allowing them to play a basic Beatdown strategy. They primarily depend on sneak tactics by being placed in face-down Attack Position, something not possible anywhere in the entire game without " ." All Darkfin monsters have the effect "This card may be Set in Attack Position." allowing them to use their effects, most of which activate upon being flipped face-up while in face-down Attack Position. Most of their support cards can flip them into face-down Attack Position or require face-down Attack Position monsters to use. They thrive under the Field Spell "Dark Ocean," which can flip them into the needed position and keep monsters in that position safe from being destroyed by card effects (as well as a 300 ATK boost). Darkfins only possess either 0 or 100 DEF apiece, making a defensive game difficult, if not impossible, but these low DEF scores allow them to be searched by some of their support cards.
However, any cards that work against face-down cards can cripple this Deck. Cards like "" and " " can completely shut down this Deck's tactics, as they depend on being face-down (in the case of the former, however, any monsters already face-down stay that way, as the card states that the monsters must be in Defense Position, which rarely occurs with Darkfins).
Darkfin Shark - Darkfin Piranha - Darkfin Mermaid - Darkfin Manta - Darkfin Pikeman - Darkfin Eel - Darkfin Jellyfish - Darkfin Orca - Darkfin Tortoise - Darkfin Angler - Darkfin Hunter - Darkfin Coela - Darkfin Dolphin - Darkfin Carp - Darkfin Puffer - Darkfin Manatee - Darkfin Dragon