Borrowed the idea for this deck from Dev over at SBMTG but added a couple of little of my own tweaks to it.

The basic idea of the deck is to use Herald of Secret Streams's ability to make the majority of the creatures unblockable because, like Merfolk Branchwalker they get +1 counters through their Explore ability or are given them +1 counters with Metallic Mimic, River Heralds' Boon or Verdurous Gearhulk.

You can also flood the field with Merfolk tokens from Deeproot Waters, which can get buffs from the Metallica Mimics.

Kopala, Warden of Waves also acts as deterrent against a lot of basic removal like Lightning Strike & Vraska's Contempt but doesn't push Magma Spray or Fatal Push beyond simple cost range.

Game 1 is really strong, especially since opponents can't use Walk the Plank to kill your merfolk creatures but it lacks in the later games when better removal is sided in.Need to make a much stronger sideboard with counterspells & maybe add in a better late game high drop creature as an alternative win-con.

Changes:Added Nissa, Steward of Elements for testing because at any point on curve she can help filter the deck & put Explore creatures or the Gearhulks on field more easily.