Mermails has reached into yet another set of combos to toolbox! When September 2013 format began, it was rather rough to see that dragons were still at the very top of all the decks early off in the format. Mermail players (including myself) were not very pleased at how much pressure Mermails were unable to put on (mainly Dragon Rulers) reverting back to mono mermail, and other mermail builds that were thought to have potential against the top tier of the format. After various testing, the Bahamut Shark Mermail deck was created, and has shown great promise for keeping up with the meta-game!
 
This new mermail variant can almost remind you of Wind-Ups pulling out 3-4 XYZ starting off and having 3 cards left in hand to set-up for the next turn. Like wind-ups and Magi-Shark, all mermails need is Mermail Abyssteus + Aqua Spirit in hand, or many other set of cards to combo your way into a field of : Bahamut Shark + Mermail Abysstrite + Mechquipped Angineer, with most of the time 3 cards in your hand. Pretty good right? So, I'm going to start with the Deck build, and then move on to basic combos.
 
Main Cards
 
 
 
Mermail Abyssteus (Level 7, Water, Aqua)
 
You can discard 1 other WATER monster to the Graveyard; Special Summon this card from your hand. When you do: Add 1 Level 4 or lower "Mermail" monster from your Deck to your hand. You can only use this effect of "Mermail Abyssteus" once per turn.
 
This has been the strongest core card in the maindeck. You get to search out Abyssocea, or search for a pike to open up your plays. This is the most consistent card to get you right into the Bahamut Shark Play. Run 3
 
Mermail Abyssocea (Level 3, Water, Aqua) 
 
 
You can target 1 "Mermail" monster you control; Special Summon any number of Level 4 or lower "Mermail" monsters from your Deck whose combined Levels are less than or equal to the Level of that monster, then send that monster to the Graveyard. You can only use the effect of "Mermail Abyssocea" once per turn.
 
This card opens up your Bahamut shark combo. You target your monster (most the time a lv 7) to bring out a lv 3 mermail and a lv 4 mermail if you choose to, 2 lv 3 mermails, 1 lv 4 mermail, 1 lv 3 mermail, or even 1 lv 7 mermail monster. Ocea can even target herself, and "transform" into a Mermail Abysslinde. Take note that if you summon pike or sturge, you can't activate their effects as they mistime do to "then send that monster to the graveyard" clause of Mermail Abyssocea.
 
Mermail Abysspike (Level 4, Water, Fish)
 
When this card is Normal or Special Summoned: You can discard 1 WATER monster to the Graveyard; add 1 Level 3 WATER monster from your Deck to your hand. You can only use the effect of "Mermail Abysspike" once per turn.
 
Abysspike is one of the core cards of the deck. You get to play out atlantean monsters and get searches to combo into more cards, or setup for turns to come. You also can bait out backrow with this card, and put pressure on your opponent to force them to react a certain way. Run 3
 
Mermail Abysslinde (Level 3, Water, Aqua)
 
If this card on the field is destroyed and sent to the Graveyard: You can Special Summon 1 "Mermail" monster from your Deck, except "Mermail Abysslinde". You can only use the effect of "Mermail Abysslinde" once per turn.
 
This card essentially can transform into any mermail you want from your deck to set-up plays. It can be used to put pressure as it "floats" throughout the game. Stops OTK plays, and best off all it makes Abyssphere live. Run 3.
 
Mermail Abyssgunde (Level 3, Water, Aqua)
 
If this card is discarded to the Graveyard: You can target 1 "Mermail" monster in your Graveyard, except "Mermail Abyssgunde"; Special Summon that target. You can only use the effect of "Mermail Abyssgunde" once per turn.
 
A mermail card that allows you to effectively control your hand and graveyard. It brings back monsters to set-up for bahamut shark plays. Can allow you to loop pike, Level 7 mermails, and set-up for XYZ plays. Run 2-3.
 
Mermail Abyssleed (Level 7, Water, Sea Serpent)
 
You can discard 3 other WATER monsters to the Graveyard; Special Summon this card from your hand. When you do: You can target 1 "Abyss-" Spell/Trap Card in your Graveyard; add that target to your hand. You can Tribute 1 other face-up Attack Position "Mermail" monster; send 1 random card from your opponent's hand to the Graveyard. You can only use this effect of "Mermail Abyssleed" once per turn.
 
Still a great card to run in this deck. You can get rid of hand prescence, get rid of threats that don't exceed (mainly 2500) enough Attack to get over you. Can also set up rank 7 plays. Run 1.
 
Mermail Abyssmegalo (Level 7, Water, Sea Serpent)
 
You can discard 2 other WATER monsters to the Graveyard; Special Summon this card from your hand. When you do: You can add 1 "Abyss-" Spell/Trap Card from your Deck to your hand. You can Tribute 1 other face-up Attack Position WATER monster; this card can make a second attack during each Battle Phase that turn.
 
Megalo has certainly fell off the charts as an extremely important card compared to Teus, but it still has its values. Getting rid of threats by discarding 2 cards and comboing with cards like Gunde for rank 7 plays. Can be used to trigger atlanteans before the battle phase, and still can be used to get the huge damage or even possibly OTK early game. Not to mention this card with can get you out of situations. For Example, "Stardust Dragon". Combo-ing with infantry as Stardust has to directly chain to infant to negate it. Run 2
 
Mermail Abyssturge ( Level 4, Water, Fish)
 
When this card is Normal or Special Summoned: You can discard 1 WATER monster to the Graveyard, then target 1 Level 3 or lower WATER monster in your Graveyard; add that target to your hand. You can only use the effect of "Mermail Abyssturge" once per turn.
 
 
Mermail abyssturge essentially gives you a 2nd "pike". You can re-loop and set-up cards like infant and gunde for following turns. Bring out more xyz options for rank 7s and ranks 4s; moreover, you can even defend for the battlephase and prevent your opponent from pushing through for game! Run 1.
 
Aqua Spirit (Level 4, Water, Aqua)
 
This card cannot be Normal Summoned or Set. This card can only be Special Summoned by removing 1 WATER monster in your Graveyard from play. During each of your opponent's Standby Phases, you can change the battle position of 1 of your opponent's face-up Monster Cards. Once changed, the monster must remain in this position for the rest of the turn.
 
 
This opens up your 1st turn XYZ rank 4 options. The 2nd effect isn't as much needed, but it helps when you are in pressured positions. For example, switching Ophion to defense in standby phase to get rid of it next turn, or holding off bosses such as Crimson Blader. Run 2-3.
 
Tidal, Dragon Ruler of Waterfalls (Level 7, Water, Dragon)
 
If this card is in your hand or Graveyard: You can banish a total of 2 WATER and/or Dragon-Type monsters from your hand and/or Graveyard, except this card; Special Summon this card. During your opponent's End Phase, if this card was Special Summoned: Return it to the hand. You can discard this card and 1 WATER monster to the Graveyard; send 1 monster from your Deck to the Graveyard. If this card is banished: You can add 1 WATER Dragon-Type monster from your Deck to your hand. You can only use 1 "Tidal, Dragon Ruler of Waterfalls" effect per turn, and only once that turn.
 
This monster allows you to make more rank 7 plays, and push for game easier. If you use its effect to dump a monster from your deck, discarding atlanteans or mermail abyssgunde, you can trigger their effects. Run 3
 
Bahamut Shark (Rank 4, Water, Sea Serpent)
 
2 Level 4 WATER monsters
Once per turn: You can detach 1 Xyz Material from this card; Special Summon 1 Rank 3 or lower WATER Xyz Monster from your Extra Deck. This card cannot attack for the rest of this turn.
 
This card allows you to special summon Abysstrite from your extra, or other cards like Acid Golem if you tech it. This is one of the most relevant extra deck cards as it allows you to build walls and maintain pressure on the field with a boss. Take note that you can attack with Bahamut Shark and activate its effect in Main Phase 2 because of  "this card cannot attack for the rest of this turn" clause. Run 1
 
Mermail Abysstrite (Rank 3, Water, Sea Serpent)
 
During either player's turn, when your opponent targets exactly 1 face-up "Mermail" monster you control for an attack, or with a Spell/Trap effect that could have targeted this card (except during the Damage Step): You can detach 1 Xyz Material from this card; that attack/effect now targets this card. When this card is destroyed and sent to the Graveyard: You can target 1 "Mermail" monster in your Graveyard, except "Mermail Abysstrite"; Special Summon that target.
 
 
This is another relevant extra in Bahamut Shark Mermails. Not only does it have 2800 defense that blader can't get over alone, it also allows you to Special summon Mermail monsters in the grave. It also doesn't have a once per turn clause in its card text, which means you can loop 2 of them and put more pressure on the board. Run 2
 
Mechquipped Angineer (Rank 3, Light, Fairy)
 
2 Level 3 monsters
Once per turn, during either player's turn: You can detach 1 Xyz Material from this card, then target 1 face-up Attack Position monster you control; change it to face-up Defense Position, and if you do, it cannot be destroyed by battle or by card effects this turn.
 
 
The last part of the bahamut shark combo to complete it. This card protects you from blader, as well as protects your bahamut shark to special summon another XYZ from your extra. You can activate it during both players turns, and it makes your field difficult to play around. Run 1
 
Leviair the Sea Dragon (Rank 3, Wind, Aqua)
 
2 Level 3 monsters
Once per turn: You can detach 1 Xyz Material from this card to target 1 banished Level 4 or lower monster; Special Summon that target to your side of the field.
 
This card allows you to combo with the monsters banished, and opens more XYZ Options. Run 1
 
 
Other Main cards
 
Atlantean Infantry (run 3)
Atlantean Marksman ( run 3)
Atlanetan Dragoons (run 1)
Mermail Abyss-sphere (run 3)
Mermail Abyss-squal (run 1-2)
 
Possible Choices
 
Creature Swap
Acid Golem
 
Sample Combos:
 
Mermail Abyssteus + Aqua Spirit + one water monster in hand
 
 
-Activate Abyssteus in hand and SS in defense mode.
 
-Search abyssocea and normal summon in attack mode.
 
-Activate ocea's effect on teus and special summon mermail abysspike and mermail abysslinde.
 
-Banish the teus now sent in the grave and special summon Aqua Spirit.
 
-Overlay pike with spirit for Bahamut Shark in attack mode. 
 
-Bahamut shark effect > Mermail Abysstrite in defense mode.
 
-Overlay mermail abysslinde and abyssocea into Mechquipped in attack mode.
 
You now have 3 monsters on the field and 3 cards left in your hand. If possible, you can even field a rank 7 along with it, and make 4 powerful XYZ plays. Pretty cool right?
There are some other combos you can make to eventually field this as well. Here are some sample combos (quoted) for OTKS.
 
"Leviair+Marksman+Tidal+Pike
 
Cards needed: Mermail Abyssteus, Atlantean Marksman, access to Tidal, Dragon Ruler of Waterfalls (in hand or grave)
-Discard Marksman to summon Abyssteus
 
-Activate Abyssteus effect, search Mermail Abyssocea
 
-Normal Summon Abyssocea, use effect to transform Mermail Abyssteus into Mermail Abysspike and any level 3 Mermail
 
-Banish Marksman and Abyssteus from the grave to Special Summon Tidal
 
-Xyz Summon Leviair the Sea Dragon with Ocea and the level 3 Mermail
 
-Activate Leviair effect to retrieve Atlantean Marksman
 
-When Marksman attacks, summon Dragoons from the deck
2600+1800+1600+1400+1800=9200 damage
 
(bonus: if opponent had a monster on board between 1300 and 2000 attack on board, you can still complete the OTK by making Gagaga Cowboy in defense using Dragoons and Abysspike)" (DGZ- Canasian)
 
"Leviair+Marksman+Abyss Dweller
 
Cards needed: Mermail Abyssteus, Atlantean Marksman, Aqua Spirit
 
-Discard Marksman to summon Abyssteus
 
-Activate Abyssteus effect, search Mermail Abyssocea
 
-Normal Summon Abyssocea, use effect to transform Mermail Abyssteus into any level 4 Mermail and any level 3 Mermail
 
-Banish Marksman from the grave to Special Summon Aqua Spirit
 
-Xyz Summon Abyss Dweller with the level 4 Mermail and Aqua Spirit
 
-Xyz Summon Leviair the Sea Dragon with Ocea and the level 3 Mermail
 
-Activate Leviair effect to retrieve Atlantean Marksman
 
-When Marksman attacks, summon Dragoons from the deck
1800+1900+2200+2300=8200 damage" (DGZ- Canasian)
 
 
Deck Skeleton
 
Monsters
 
3x Mermail Abyssteus
3x Mermail Abysspike
3x Mermail Abysslinde
2x Mermail Abyssmegalo
2x Mermail Abyssgunde
1x Meramil Abyssocea
1x Mermail Abyssturge
3x Atlantean Infantry
3x Atlantean Marksman
3x Atlantean Infantry
2-3x Aqua Spirit
3x Dragon Ruler Tidal
 
Traps
 
3x Mermail Abyss-sphere
1-2x Meramil Abyss-squall
 
Extra
1x Bahamut Shark
2x Mermail Abysstrite
1x Mechquipped Angineer
1x Leviair the Sea Dragon
 
Strengths
 

• Has some sort of ability to pull off OTKS.
  
  
  
  
• Maintains pressure on the board by looping summons and effects.
  
  
  
  
• Explosive effects through monsters to put pressure in the game.
  
  
  
  
• Skilled in keeping a few monsters "floating" to handle slower decks.
  
  
  
  
  
  

 
Weaknesses
 

• Relies on combos and special summoning to get through.
  
  
  
  
• Most of the cards rely on grave-setups and having to be sent to the grave to trigger effects.
  
  
  
  
• Not strong in the "defensive" game when many bosses linger the field, and struggles to deal with "floaters".
  
  
  
  
• Lack of many blowouts in comparison to E-dragons.
  
  
  
  
  
  

 
Siding
 
Rivalry of the Warlords- Prevents you from making diverse options and plays. You are limited to Sea Serpent, Fish, aqua, or even Dragons at times when you make big fields.
 
Dimension Fissure & Macro Cosmos - You can't activate any mermail effects, and no atlanteans can be discarded to trigger in the grave. With the exception of detaching with XYZ monsters (dimensional fissure only).
 
Maxx "C" - This prevents you from comboing into your big plays. It leaves you open a bit, and puts huge pressure on you.

Soul Drain - Can't activate any effects that trigger in the graveyard such as linde, gunde or any atlantean effects. You can't use tidal, and options are severely limited. Hard to put pressure on the board.
 
Thunder King Rai-oh- you can't search any cards, and have to play around TKR before you can make huge plays.
 
Mind Crush- Hit cards in hand and prevent them from resolving. (IE Opponent activates Teus, and you chain Mind Crush discarding Teus in hand). Bonus you get to check the opponents hand as long as all copies (3) aren't already known in the gamestate.
 
Debunk- Negate monsters that activate in the hand such as megalo and tidal, as well as monsters that activate in the graveyard. Abysslinde and Tidal.
 
What Bahamut Mermails can side
 
Chain Whirlwind - Nutty card to run this format. You can destroy 2 spell cards on the field when a spell or trap is destroyed by a card effect. You can use this on End Phase Abyss-spheres or even after the resolution of using mst and blowing up 2 more of your opponent's backrow. It leaves your opponent vulnerable.
 
Skill Drain- Mermail effects can still be activated. Atlantean effects trigger in the grave. Kill your opponent that relies on effects on the field to maintain presence (Fire Fists), and decks like Evilswarm so Ophion doesn't hinder your plays.
 
Gozen Match- Mainly for the Dragon Ruler matchup. You can also use this against decks that have more than one attribute.
 
Imperial Iron Wall- Siding out some of your banish cards like Aqua Spirit and Tidal, you can play against Dragon Rulers, and other matchups relying on Banishing such as Bujin much more easier.
 
Vanity Fiend- After making huge combos, tribute summoning this will soft lock Dragons as they can't special summon. This is also viable in the mirror match, and as long as you have this 2400 attack beatstick on the field, you can gain momentum and just setup for future plays.
 
Debunk- Can be sided for the mirror match, Dragon matchup and for cards like Maxx C, veiler, etc.
 
XYZ Encore- For Evilswarms.
 
 
Royal Decree- Destroy trap heavy decks, and make it easier to combo and put pressure on the board to possibly make OTKS and take the game faster.

nice guide katana

Edited...forgot Soul Drain x.x