U/B Merfolk
A Modern deck, by Strong Sad
2nd place at a tournament in Magic Online on 2013-11-03

Maindeck:

Artifacts
4 Aether Vial

Creatures
4 Cursecatcher
4 Lord of Atlantis (Not currently legal in Modern)
4 Master of the Pearl Trident
4 Master of Waves
4 Silvergill Adept

Enchantments
4 Spreading Seas

Instants
3 Dismember

Legendary Creatures
3 Kira, Great Glass-Spinner

Sorceries
4 Thoughtseize

Basic Lands
6 Island

Lands
4 Darkslick Shores
4 Misty Rainforest
4 Mutavault
4 Watery Grave

Sideboard:
2 Grafdigger's Cage
3 Spellskite
3 Threads of Disloyalty
3 Hurkyl's Recall
3 Swan Song
1 Vendilion Clique