Merfolk
A Modern deck, by Daniel Duffee
3rd place at a tournament in Syracuse, New York, United States on 2017-08-05

Maindeck:

Artifacts
4 Aether Vial
2 Smuggler's Copter

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

Enchantments
4 Spreading Seas

Instants
3 Dismember

Legendary Creatures
2 Vendilion Clique

Basic Lands
12 Island

Lands
2 Cavern of Souls
4 Mutavault

Legendary Lands
1 Minamo, School at Water's Edge
1 Oboro, Palace in the Clouds

Sideboard:
3 Relic of Progenitus
3 Ceremonious Rejection
2 Dispel
1 Echoing Truth
2 Hurkyl's Recall
2 Negate
2 Unified Will