The goal of the deck is to go wide, and to defend our threats cheaply and efficiently with 10 counter effects that attack spells and effects from various angles.
Atlantis Shuffle with some sideboard ideas can be seen below as a screenshot from MTG Arena:

I’d cut a card, probably Mikey #3 for a 4th Multiversal Passage. I’d consider cutting the Island for a Cavern of Souls. I’d probably cut 1 Leviathan for a 3rd Sage, and sideboard a temple garden cutting a Wan Shi Tong.
Sideboarding, very straight forward:
- Oko and Leviathan vs Spellementals
- Wan and Wistful vs Mono Green
- 3 Sage vs Prowess, and depending on their build you may want Wan and or Wistfulness
Atlantis Shuffle with some sideboard ideas cab be seen below as a text export to and from MTG Arena:
Deck
4 Botanical Sanctum (OTJ) 267
4 Breeding Pool (EOE) 251
3 Multiversal Passage (OM1) 181
4 Starting Town (FIN) 289
4 Ouroboroid (EOE) 201
4 Tishana’s Tidebinder (LCI) 81
3 Detect Intrusion (OM1) 28
4 Badgermole Cub (TLA) 167
3 Michelangelo, Weirdness to 11 (TMT) 121
4 Druneth, Reviver of the Hive (OM1) 136
1 Repulsive Mutation (MKM) 227
3 Mindspring Merfolk (DFT) 51
1 Spell Pierce (DFT) 64
3 Three Steps Ahead (OTJ) 75
3 Cenote Scout (LCI) 178
3 Gene Pollinator (EOE) 186
4 Llanowar Elves (M19) 314
3 Mockingbird (BLB) 61
1 Island (ANA) 3
1 Forest (ANA) 9
Sideboard
3 Wan Shi Tong, Librarian (TLA) 78
2 Oko, Lorwyn Liege (ECL) 61
2 Sage of the Skies (TDM) 22
3 Wistfulness (ECL) 252
3 Summon: Leviathan (FIN) 77
Cards to Highlight
Mindspring, Cenote, Druneth/ Jackal, Mocking bird, as they are key cards that aren’t seen often in other decks.
Mindspring Merfolk
Mindspring sets you up for future success, if it lives to to turn 4 or so its a huge asset.

Cenote Scout
Cenote gives you an immediate threat, and digs for what you’ll want next.

Mockingbird
Mockingbird can be used early, or hang out on the sidelines, or copy their guy and also be returned with spider sense.

Druneth/ Jackal
Druneth is Druneth.

Michelangelo
Michelangelo plays a very nice role.

Ouroboroid
Ouroboroid is our bae.
