Have

Spirebluff Canal

This land enters tapped unless you control two or fewer other lands.
{T}: Add {U} or {R}.

Reckless Pyrosurfer

Haste
Landfall — Whenever a land you control enters, this creature gains battle cry until end of turn. (Whenever this creature attacks, each other attacking creature gets +1/+0 until end of turn. Each instance of battle cry triggers separately.)

Mountain

High Seas

Red creature spells and green creature spells cost {1} more to cast.

Tidal Wave

Create a 5/5 blue Wall creature token with defender. Sacrifice it at the beginning of the next end step.

Island

Getting

Leyline of Anticipation

If this card is in your opening hand, you may begin the game with it on the battlefield.
You may cast spells as though they had flash.

Calamitous Tide

Return up to two target creatures to their owners' hands. Draw two cards, then discard a card.

Master of Waves

Protection from red
Elemental creatures you control get +1/+1.
When this creature enters, create a number of 1/0 blue Elemental creature tokens equal to your devotion to blue. (Each {U} in the mana costs of permanents you control counts toward your devotion to blue.)

Sword of War and Peace

Equipped creature gets +2/+2 and has protection from red and from white.
Whenever equipped creature deals combat damage to a player, this Equipment deals damage to that player equal to the number of cards in their hand and you gain 1 life for each card in your hand.
Equip {2}

Training Center

This land enters tapped unless you have two or more opponents.
{T}: Add {U} or {R}.

Accorder's Shield

Equipped creature gets +0/+3 and has vigilance. (Attacking doesn't cause it to tap.)
Equip {3} ({3}: Attach to target creature you control. Equip only as a sorcery.)

Rapid Hybridization

Destroy target creature. It can't be regenerated. That creature's controller creates a 3/3 green Frog Lizard creature token.

Steam Vents

({T}: Add {U} or {R}.)
As this land enters, you may pay 2 life. If you don't, it enters tapped.

Sudden Storm

Tap up to two target creatures. Those creatures don't untap during their controllers' next untap steps. Scry 1. (Look at the top card of your library. You may put that card on the bottom.)

Kopala, Warden of Waves

Spells your opponents cast that target a Merfolk you control cost {2} more to cast.
Abilities your opponents activate that target a Merfolk you control cost {2} more to activate.

Displacement Wave

Return all nonland permanents with mana value X or less to their owners' hands.

Wavecrash Triton

Heroic — Whenever you cast a spell that targets this creature, tap target creature an opponent controls. That creature doesn't untap during its controller's next untap step.

Master of the Pearl Trident

Other Merfolk creatures you control get +1/+1 and have islandwalk. (They can't be blocked as long as defending player controls an Island.)

Arcane Signet

{T}: Add one mana of any color in your commander's color identity.

Merrow Wavebreakers

{1}{U}, {Q}: This creature gains flying until end of turn. ({Q} is the untap symbol.)

Ponder

Look at the top three cards of your library, then put them back in any order. You may shuffle.
Draw a card.

Shivan Reef

{T}: Add {C}.
{T}: Add {U} or {R}. This land deals 1 damage to you.

Enter the Enigma

Target creature can't be blocked this turn.
Draw a card.

Blue Elemental Blast

Choose one —
• Counter target red spell.
• Destroy target red permanent.

Flame Wave

Flame Wave deals 4 damage to target player or planeswalker and each creature that player or that planeswalker's controller controls.

Mardu Scout

Dash {1}{R} (You may cast this spell for its dash cost. If you do, it gains haste, and it's returned from the battlefield to its owner's hand at the beginning of the next end step.)

Triton Waverider

Constellation — Whenever an enchantment you control enters, this creature gains flying until end of turn.

Sea's Claim

Enchant land (Target a land as you cast this. This card enters attached to that land.)
Enchanted land is an Island.

Chandra's Flame Wave

Chandra's Flame Wave deals 2 damage to target player and each creature that player controls. Search your library and/or graveyard for a card named Chandra, Flame's Fury, reveal it, and put it into your hand. If you search your library this way, shuffle.

Tidal Surge

Tap up to three target creatures without flying.

Wall of Water

Defender (This creature can't attack.)
{U}: This creature gets +1/+0 until end of turn.

Tidal Courier

When this creature enters, reveal the top four cards of your library. Put all Merfolk cards revealed this way into your hand and the rest on the bottom of your library in any order.
{3}{U}: This creature gains flying until end of turn.

Nyxborn Seaguard

Wave Goodbye

Return each creature without a +1/+1 counter on it to its owner's hand.

Stormcarved Coast

This land enters tapped unless you control two or more other lands.
{T}: Add {U} or {R}.

Sulfur Falls

This land enters tapped unless you control an Island or a Mountain.
{T}: Add {U} or {R}.

Daring Waverider

When this creature enters, you may cast target instant or sorcery card with mana value 4 or less from your graveyard without paying its mana cost. If that spell would be put into your graveyard, exile it instead.

Shield of Kaldra

Equipment named Sword of Kaldra, Shield of Kaldra, and Helm of Kaldra have indestructible.
Equipped creature has indestructible. (Damage and effects that say "destroy" don't destroy it.)
Equip {4}

Kite Shield

Equipped creature gets +0/+3.
Equip {3} ({3}: Attach to target creature you control. Equip only as a sorcery.)

Eluge, the Shoreless Sea

Eluge's power and toughness are each equal to the number of Islands you control.
Whenever Eluge enters or attacks, put a flood counter on target land. It's an Island in addition to its other types for as long as it has a flood counter on it.
The first instant or sorcery spell you cast each turn costs {U} (or {1}) less to cast for each land you control with a flood counter on it.

Expedite

Target creature gains haste until end of turn.
Draw a card.

Sol Ring

Hydroblast

Choose one —
• Counter target spell if it's red.
• Destroy target permanent if it's red.

Volcanic Island

High Tide

Until end of turn, whenever a player taps an Island for mana, that player adds an additional {U}.

Run Ashore

Choose one or both —
• The owner of target nonland permanent puts it on their choice of the top or bottom of their library.
• Return target nonland permanent to its owner's hand.

Valley Floodcaller

Flash
You may cast noncreature spells as though they had flash.
Whenever you cast a noncreature spell, Birds, Frogs, Otters, and Rats you control get +1/+1 until end of turn. Untap them.

Sea Sprite

Triton Wavebreaker

Bestow {1}{U} (If you cast this card for its bestow cost, it's an Aura spell with enchant creature. It becomes a creature again if it's not attached.)
As long as this permanent is a creature, it has prowess. (Whenever you cast a noncreature spell, this creature gets +1/+1 until end of turn.)
Enchanted creature gets +1/+1 and has prowess.

Talrand, Sky Summoner

Whenever you cast an instant or sorcery spell, create a 2/2 blue Drake creature token with flying.

Storm King's Thunder

When you next cast an instant or sorcery spell this turn, copy that spell X times. You may choose new targets for the copies.

Molten Tributary

({T}: Add {U} or {R}.)
This land enters tapped.

Ominous Seas

Whenever you draw a card, put a foreshadow counter on this enchantment.
Remove eight foreshadow counters from this enchantment: Create an 8/8 blue Kraken creature token.
Cycling {2} ({2}, Discard this card: Draw a card.)

Waterfall Aerialist

Flying
Ward {2} (Whenever this creature becomes the target of a spell or ability an opponent controls, counter it unless that player pays {2}.)

Fishliver Oil

Enchant creature (Target a creature as you cast this. This card enters attached to that creature.)
Enchanted creature has islandwalk. (It can't be blocked as long as defending player controls an Island.)

Spreading Seas

Enchant land
When this Aura enters, draw a card.
Enchanted land is an Island.

Water Wings

Until end of turn, target creature you control has base power and toughness 4/4 and gains flying and hexproof. (It can't be the target of spells or abilities your opponents control.)

Shore Up

Target creature you control gets +1/+1 and gains hexproof until end of turn. Untap it. (It can't be the target of spells or abilities your opponents control.)

Flame Rift

Flame Rift deals 4 damage to each player.

Ferrous Lake

Otterball Antics

Create a 1/1 blue and red Otter creature token with prowess. If this spell was cast from anywhere other than your hand, put a +1/+1 counter on that creature. (Whenever you cast a noncreature spell, a creature with prowess gets +1/+1 until end of turn.)
Flashback {3}{U} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Heat Wave

Cumulative upkeep {R} (At the beginning of your upkeep, put an age counter on this permanent, then sacrifice it unless you pay its upkeep cost for each age counter on it.)
Blue creatures can't block creatures you control.
Nonblue creatures can't block creatures you control unless their controller pays 1 life for each blocking creature they control.

Shield of the Avatar

If a source would deal damage to equipped creature, prevent X of that damage, where X is the number of creatures you control.
Equip {2} ({2}: Attach to target creature you control. Equip only as a sorcery.)

Field Research

Kicker {2}{U} (You may pay an additional {2}{U} as you cast this spell.)
Draw two cards. If this spell was kicked, draw three cards instead.

Captain Howler, Sea Scourge

Ward—{2}, Pay 2 life.
Whenever you discard one or more cards, target creature gets +2/+0 until end of turn for each card discarded this way. Whenever that creature deals combat damage to a player this turn, you draw a card.

Risen Riptide

Whenever you cast a kicked spell, this creature has base power and toughness 5/5 until end of turn.

Part Water

X target creatures gain islandwalk until end of turn. (They can't be blocked as long as defending player controls an Island.)

Merfolk Spy

Islandwalk (This creature can't be blocked as long as defending player controls an Island.)
Whenever this creature deals combat damage to a player, that player reveals a card at random from their hand.

Mana Geyser

Add {R} for each tapped land your opponents control.

Bria, Riptide Rogue

Prowess (Whenever you cast a noncreature spell, this creature gets +1/+1 until end of turn.)
Other creatures you control have prowess. (If a creature has multiple instances of prowess, each triggers separately.)
Whenever you cast a noncreature spell, target creature you control can't be blocked this turn.

Swan Song

Counter target enchantment, instant, or sorcery spell. Its controller creates a 2/2 blue Bird creature token with flying.

Cathar's Shield

Equipped creature gets +0/+3 and has vigilance.
Equip {3} ({3}: Attach to target creature you control. Equip only as a sorcery.)