Mermails        
3 Pike              
2 Megalo          
2 Linde            
2 Gunde           
1 Teus
1 Leed

Atlanteans
3 Prince
2 Marksman
2 Dragoons
2 Infantry

Others
3 Deep Sea Diva
2 Ghost Ogre & Snow Rabbit

Spells
1 Pot of Avarice
1 Monster Reborn
1 Soul Charge
1 Instant Fusion
1 One for One
1 Harpie's Feather Duster

Traps
2 Abyss-Sphere
2 Torrential Tribute
2 Mind Crush
1 Compulsory Evacuation Device
1 Solemn Warning
1 Vanity's Emptiness 

Extra
1 Elder God Noden
1 Trishula, Dragon of the Ice Barrier 
1 Gungir, Dragon of the Ice Barrier
1 Dewloren, Tiger King of the Ice Barrier
1 Leo, the Keeper of the Sacred Tree
1 Hot Red Dragon Archfiend
1 Crimson Blader
1 Clear Wing Synchro Dragon
1 Mermail Abyssgaios
1 Mecha Phantom Beast Dracossack
1 Big Eye
2 Number 101: Silent Honor ARK
1 Evilswarm Exciton Knight
1 Abyss Dweller

 Works pretty well, your ideal starting hand would be ether a hand that can summon or search Prince. Having Deep Sea Diva + 2 water monsters I would say is the ideal hand to start with.
 Noden is very useful in this deck (As in every deck out there), most cases you will be using him for synchro summoning. I like using it to bring back Diva and then fusing into Trishula/Leo.

I personally prefer the Undine build for OCG Mermails.

- COTH, - 1 Galaxy Cyclone (no point to just having 1 imo)
+ 3 Torrential (needs torrentials in this spammy meta :p)

-I dislike Udine, for he generates dead weight cards. Prince with Diva virtualy does the same thing, cept it adds a water monster to abuse.

-Could you please tell me what is meta in OCG in this format; I am a bit outdated? Last time I played in OCG compulse was the mvp card.

Well 1 Genex Controller + 2 Undine just brings more stability, old argument of consistency vs explosiveness.

Meta wise, its Nekroz, and decks with floodgates. Since you are using Mermails, a torrential can lead to easy OTKS. This is preference of course, I just like torrential to stop Nekroz locks (hell I even main 3 Eclipse in some decks) since CED can be negated by Trishula (which is run at 2) and not many people run Gungnir anymore.

Ah I see, Imma swap out 1 Compuls and Cyclone for Torrential. I am keeping CotH tho.