Temple of the False God

{T}: Add {C}{C}. Activate only if you control five or more lands.

Ichthyomorphosis

Enchant creature
Enchanted creature loses all abilities and is a blue Fish with base power and toughness 0/1.

Drowned Secrets

Whenever you cast a blue spell, target player mills two cards.

Man-o'-War

When Man-o'-War enters the battlefield, return target creature to its owner's hand.

Colossal Whale

Islandwalk (This creature can't be blocked as long as defending player controls an Island.)
Whenever Colossal Whale attacks, you may exile target creature defending player controls until Colossal Whale leaves the battlefield. (That creature returns under its owner's control.)

Charix, the Raging Isle

Spells your opponents cast that target Charix, the Raging Isle cost {2} more to cast.
{3}: Charix gets +X/-X until end of turn, where X is the number of Islands you control.

Shark Typhoon

Whenever you cast a noncreature spell, create an X/X blue Shark creature token with flying, where X is that spell's mana value.
Cycling {X}{1}{U} ({X}{1}{U}, Discard this card: Draw a card.)
When you cycle Shark Typhoon, create an X/X blue Shark creature token with flying.

Thassa's Emissary

Bestow {5}{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 to a creature.)
Whenever Thassa's Emissary or enchanted creature deals combat damage to a player, draw a card.
Enchanted creature gets +3/+3.

Myriad Landscape

Myriad Landscape enters the battlefield tapped.
{T}: Add {C}.
{2}, {T}, Sacrifice Myriad Landscape: Search your library for up to two basic land cards that share a land type, put them onto the battlefield tapped, then shuffle.

Gush

You may return two Islands you control to their owner's hand rather than pay this spell's mana cost.
Draw two cards.

Spreading Seas

Enchant land
When Spreading Seas enters the battlefield, draw a card.
Enchanted land is an Island.

Staff of the Mind Magus

Whenever you cast a blue spell or an Island enters the battlefield under your control, you gain 1 life.

Sky Diamond

Sky Diamond enters the battlefield tapped.
{T}: Add {U}.

Crush of Tentacles

Surge {3}{U}{U} (You may cast this spell for its surge cost if you or a teammate has cast another spell this turn.)
Return all nonland permanents to their owners' hands. If this spell's surge cost was paid, create an 8/8 blue Octopus creature token.

Killer Whale

{U}: Killer Whale gains flying until end of turn.

Lorthos, the Tidemaker

Whenever Lorthos, the Tidemaker attacks, you may pay {8}. If you do, tap up to eight target permanents. Those permanents don't untap during their controllers' next untap steps.

Fleet Swallower

Whenever Fleet Swallower attacks, target player mills half their library, rounded up.

Pouncing Shoreshark

Mutate {3}{U} (If you cast this spell for its mutate cost, put it over or under target non-Human creature you own. They mutate into the creature on top plus all abilities from under it.)
Flash
Whenever this creature mutates, you may return target creature an opponent controls to its owner's hand.

Floodwaters

Return up to two target creatures to their owners' hands.
Cycling {2} ({2}, Discard this card: Draw a card.)

Bronze Walrus

When Bronze Walrus enters the battlefield, scry 2. (Look at the top two cards of your library, then put any number of them on the bottom of your library and the rest on top in any order.)
{T}: Add one mana of any color.

Pyramid of the Pantheon

{2}, {T}: Add one mana of any color. Put a brick counter on Pyramid of the Pantheon.
{T}: Add three mana of any one color. Activate only if there are three or more brick counters on Pyramid of the Pantheon.

Eaten by Piranhas

Flash
Enchant creature
Enchanted creature loses all abilities and is a black Skeleton creature with base power and toughness 1/1. (It loses all other card types and creature types.)

Cold-Water Snapper

Hexproof (This creature can't be the target of spells or abilities your opponents control.)

Eel Umbra

Flash (You may cast this spell any time you could cast an instant.)
Enchant creature
Enchanted creature gets +1/+1.
Totem armor (If enchanted creature would be destroyed, instead remove all damage from it and destroy this Aura.)

Ancient Crab

Thought Sponge

Flash
Thought Sponge enters the battlefield with a number of +1/+1 counters on it equal to the greatest number of cards an opponent has drawn this turn.
When Thought Sponge dies, draw cards equal to its power.

Retreat to Coralhelm

Landfall — Whenever a land enters the battlefield under your control, choose one —
• You may tap or untap target creature.
• Scry 1. (Look at the top card of your library. You may put that card on the bottom of your library.)

Nyx Lotus

Nyx Lotus enters the battlefield tapped.
{T}: Choose a color. Add an amount of mana of that color equal to your devotion to that color. (Your devotion to a color is the number of mana symbols of that color in the mana costs of permanents you control.)

Nykthos, Shrine to Nyx

{T}: Add {C}.
{2}, {T}: Choose a color. Add an amount of mana of that color equal to your devotion to that color. (Your devotion to a color is the number of mana symbols of that color in the mana costs of permanents you control.)

Sinking Feeling

Enchant creature
Enchanted creature doesn't untap during its controller's untap step.
Enchanted creature has "{1}, Put a -1/-1 counter on this creature: Untap this creature."

Drag Under

Return target creature to its owner's hand.
Draw a card.

Voracious Greatshark

Flash
When Voracious Greatshark enters the battlefield, counter target artifact or creature spell.

Displacement Wave

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

Mistford River Turtle

Whenever Mistford River Turtle attacks, another target attacking non-Human creature can't be blocked this turn.

Angler Turtle

Hexproof
Creatures your opponents control attack each combat if able.

Ancient Carp

Sea God's Revenge

Return up to three target creatures your opponents control to their owners' hands. Scry 1. (Look at the top card of your library. You may put that card on the bottom of your library.)

Swirling Torrent

Choose one or both —
• Put target creature on top of its owner's library.
• Return target creature to its owner's hand.

Chromeshell Crab

Morph {4}{U} (You may cast this card face down as a 2/2 creature for {3}. Turn it face up any time for its morph cost.)
When Chromeshell Crab is turned face up, you may exchange control of target creature you control and target creature an opponent controls.

The Surgical Bay

The Surgical Bay enters the battlefield tapped.
{T}: Add {U}.
{1}{U}, {T}, Sacrifice The Surgical Bay: Draw a card.

Nezahal, Primal Tide

This spell can't be countered.
You have no maximum hand size.
Whenever an opponent casts a noncreature spell, draw a card.
Discard three cards: Exile Nezahal, Primal Tide. Return it to the battlefield tapped under its owner's control at the beginning of the next end step.

Coastal Breach

Undaunted (This spell costs {1} less to cast for each opponent.)
Return all nonland permanents to their owners' hands.

Canyon Crab

{1}{U}: Canyon Crab gets +2/-2 until end of turn.
At the beginning of your end step, if you haven't cast a spell from your hand this turn, draw a card, then discard a card.

Giant Crab

{U}: Giant Crab gains shroud until end of turn. (It can't be the target of spells or abilities.)

Waker of Waves

Creatures your opponents control get -1/-0.
{1}{U}, Discard Waker of Waves: Look at the top two cards of your library. Put one of them into your hand and the other into your graveyard.

Giant Octopus

Spined Megalodon

Hexproof (This creature can't be the target of spells or abilities your opponents control.)
Whenever Spined Megalodon attacks, scry 1. (Look at the top card of your library. You may put that card on the bottom of your library.)

Thran Dynamo

Aegis Turtle

Clutch of Currents

Return target creature to its owner's hand.
Awaken 3—{4}{U} (If you cast this spell for {4}{U}, also put three +1/+1 counters on target land you control and it becomes a 0/0 Elemental creature with haste. It's still a land.)

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.)

Crystacean

Tidal Barracuda

Any player may cast spells as though they had flash.
Your opponents can't cast spells during your turn.

High Tide

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

Gulf Squid

When Gulf Squid enters the battlefield, tap all lands target player controls.

Mantle of Tides

Equipped creature gets +1/+2.
Whenever you draw your second card each turn, attach Mantle of Tides to target creature you control.
Equip {3} ({3}: Attach to target creature you control. Equip only as a sorcery.)

Octopus Umbra

Enchant creature
Enchanted creature has base power and toughness 8/8 and has "Whenever this creature attacks, you may tap target creature with power 8 or less."
Totem armor (If enchanted creature would be destroyed, instead remove all damage from it and destroy this Aura.)

Sigiled Starfish

{T}: Scry 1. (Look at the top card of your library. You may put that card on the bottom of your library.)

Wingfold Pteron

Wingfold Pteron enters the battlefield with your choice of a flying counter or a hexproof counter on it. (A creature with hexproof can't be the target of spells or abilities your opponents control.)

Dreadwaters

Target player mills X cards, where X is the number of lands you control.

Island

Leyline of Anticipation

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

Deepglow Skate

When Deepglow Skate enters the battlefield, double the number of each kind of counter on any number of target permanents.

Kapsho Kitefins

Flying
Whenever Kapsho Kitefins or another creature enters the battlefield under your control, tap target creature an opponent controls.

Clinging Anemones

Defender
Evolve (Whenever a creature enters the battlefield under your control, if that creature has greater power or toughness than this creature, put a +1/+1 counter on this creature.)

Riptide Turtle

Sky-Eel School

Flying
When Sky-Eel School enters the battlefield, draw a card, then discard a card.

Waterwhirl

Return up to two target creatures to their owners' hands.

Skittering Crustacean

{6}{U}: Monstrosity 4. (If this creature isn't monstrous, put four +1/+1 counters on it and it becomes monstrous.)
As long as Skittering Crustacean is monstrous, it has hexproof. (It can't be the target of spells or abilities your opponents control.)

Sol Ring

Roiling Waters

Return up to two target creatures your opponents control to their owners' hands. Target player draws two cards.

Encrust

Enchant artifact or creature
Enchanted permanent doesn't untap during its controller's untap step and its activated abilities can't be activated.

Waterknot

Enchant creature
When Waterknot enters the battlefield, tap enchanted creature.
Enchanted creature doesn't untap during its controller's untap step.

Coral Atoll

Coral Atoll enters the battlefield tapped.
When Coral Atoll enters the battlefield, sacrifice it unless you return an untapped Island you control to its owner's hand.
{T}: Add {C}{U}.

Armored Whirl Turtle

Fortress Crab

Mirrorshell Crab

Ward {3} (Whenever this creature becomes the target of a spell or ability an opponent controls, counter it unless that player pays {3}.)
Channel — {2}{U}, Discard Mirrorshell Crab: Counter target spell or ability unless its controller pays {3}.