Aquamoeba

Discard a card: Switch Aquamoeba's power and toughness until end of turn.

Wall of Frost

Defender
Whenever Wall of Frost blocks a creature, that creature doesn't untap during its controller's next untap step.

Glacial Wall

Tidal Force

At the beginning of each upkeep, you may tap or untap target permanent.

Frost Breath

Tap up to two target creatures. Those creatures don't untap during their controller's next untap step.

Soul of the Rapids

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

Chronic Flooding

Enchant land
Whenever enchanted land becomes tapped, its controller mills three cards.

Living Tsunami

Flying
At the beginning of your upkeep, sacrifice Living Tsunami unless you return a land you control to its owner's hand.

Frost Walker

When Frost Walker becomes the target of a spell or ability, sacrifice it.

Whelming Wave

Return all creatures to their owners' hands except for Krakens, Leviathans, Octopuses, and Serpents.

Rising Waters

Lands don't untap during their controllers' untap steps.
At the beginning of each player's upkeep, that player untaps a land they control.

Thawing Glaciers

Thawing Glaciers enters tapped.
{1}, {T}: Search your library for a basic land card, put that card onto the battlefield tapped, then shuffle. Return Thawing Glaciers to its owner's hand at the beginning of the next cleanup step.

Chill

Ominous Seas

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

Tidewalker

Tidewalker enters with a time counter on it for each Island you control.
Vanishing (At the beginning of your upkeep, remove a time counter from this creature. When the last is removed, sacrifice it.)
Tidewalker's power and toughness are each equal to the number of time counters on it.

Waterknot

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

Scion of Glaciers

{U}: Scion of Glaciers gets +1/-1 until end of turn.

Water Servant

{U}: Water Servant gets +1/-1 until end of turn.
{U}: Water Servant gets -1/+1 until end of turn.

Boreal Elemental

Flying
Spells your opponents cast that target Boreal Elemental cost {2} more to cast.

Brackwater Elemental

When Brackwater Elemental attacks or blocks, sacrifice it at the beginning of the next end step.
Unearth {2}{U} ({2}{U}: Return this card from your graveyard to the battlefield. It gains haste. Exile it at the beginning of the next end step or if it would leave the battlefield. Unearth only as a sorcery.)

Hydroblast

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

Chillbringer

Flying
When Chillbringer enters, tap target creature an opponent controls. It doesn't untap during its controller's next untap step.

Frost Lynx

When Frost Lynx enters, tap target creature an opponent controls. That creature doesn't untap during its controller's next untap step.

Rain of Revelation

Glacial Grasp

Tap target creature. Its controller mills two cards. That creature doesn't untap during its controller's next untap step. (They put the top two cards of their library into their graveyard.)
Draw a card.

Flood of Tears

Return all nonland permanents to their owners' hands. If you return four or more nontoken permanents you control this way, you may put a permanent card from your hand onto the battlefield.

Dark Depths

Dark Depths enters with ten ice counters on it.
{3}: Remove an ice counter from Dark Depths.
When Dark Depths has no ice counters on it, sacrifice it. If you do, create Marit Lage, a legendary 20/20 black Avatar creature token with flying and indestructible.

Iceberg Cancrix

Whenever another snow permanent you control enters, you may have target player mill two cards.

Roil Elemental

Flying
Landfall — Whenever a land you control enters, you may gain control of target creature for as long as you control Roil Elemental.

Watercourser

{U}: Watercourser gets +1/-1 until end of turn.

Blizzard Elemental

Uncomfortable Chill

Creatures your opponents control get -2/-0 until end of turn.
Draw a card.

Cone of Cold

Roll a d20.
1—9 | Tap all creatures your opponents control.
10—19 | Tap all creatures your opponents control. Those creatures don't untap during their controllers' next untap steps.
20 | Tap all creatures your opponents control. Those creatures don't untap during their controllers' next untap steps. Until your next turn, creatures your opponents control enter tapped.

Halimar Depths

Halimar Depths enters tapped.
When Halimar Depths enters, look at the top three cards of your library, then put them back in any order.
{T}: Add {U}.

Flood

{U}{U}: Tap target creature without flying.

Rush of Ice

Tap target creature. It doesn't untap during its controller's next untap step.
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.)

Clearwater Goblet

Sunburst (This enters with a charge counter on it for each color of mana spent to cast it.)
At the beginning of your upkeep, you may gain life equal to the number of charge counters on Clearwater Goblet.

Tidespout Tyrant

Flying
Whenever you cast a spell, return target permanent to its owner's hand.

Octavia, Living Thesis

This spell costs {8} less to cast if you have eight or more instant and/or sorcery cards in your graveyard.
Ward {8}
Magecraft — Whenever you cast or copy an instant or sorcery spell, target creature has base power and toughness 8/8 until end of turn.

Yarok's Wavecrasher

When Yarok's Wavecrasher enters, return another creature you control to its owner's hand.

Ray of Frost

Flash
Enchant creature
When Ray of Frost enters, if enchanted creature is red, tap it.
As long as enchanted creature is red, it loses all abilities.
Enchanted creature doesn't untap during its controller's untap step.

Engulf the Shore

Return to their owners' hands all creatures with toughness less than or equal to the number of Islands you control.

Ice Cave

Whenever a player casts a spell, any other player may pay that spell's mana cost. If a player does, counter the spell. (Mana cost includes color.)

Glacial Crasher

Trample (This creature can deal excess combat damage to the player or planeswalker it's attacking.)
Glacial Crasher can't attack unless there is a Mountain on the battlefield.

Remote Isle

Remote Isle enters tapped.
{T}: Add {U}.
Cycling {2} ({2}, Discard this card: Draw a card.)

Deep Freeze

Enchant creature
Enchanted creature has base power and toughness 0/4, has defender, loses all other abilities, and is a blue Wall in addition to its other colors and types.

Brine Elemental

Morph {5}{U}{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 Brine Elemental is turned face up, each opponent skips their next untap step.

Flash Flood

Choose one —
• Destroy target red permanent.
• Return target Mountain to its owner's hand.

Whitewater Naiads

Constellation — Whenever Whitewater Naiads or another enchantment you control enters, target creature can't be blocked this turn.

Hydrosurge

Target creature gets -5/-0 until end of turn.

Frozen Solid

Enchant creature
Enchanted creature doesn't untap during its controller's untap step.
When enchanted creature is dealt damage, destroy it.

Chilling Trap

Target creature gets -4/-0 until end of turn. If you control a Wizard, draw a card.

Flashfreeze

Floodwaters

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

Waterwhirl

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

Floodhound

{3}, {T}: Investigate. (Create a Clue token. It's an artifact with "{2}, Sacrifice this artifact: Draw a card.")

Brain Freeze

Target player mills three cards.
Storm (When you cast this spell, copy it for each spell cast before it this turn. You may choose new targets for the copies.)

Roiling Waters

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

Water Elemental

Early Frost

Wall of Water

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

Tideforce Elemental

{U}, {T}: You may tap or untap another target creature.
Landfall — Whenever a land you control enters, you may untap Tideforce Elemental.

Hydrolash

Attacking creatures get -2/-0 until end of turn.
Draw a card.

Wave-Wing Elemental

Flying
Landfall — Whenever a land you control enters, Wave-Wing Elemental gets +2/+2 until end of turn.

High Seas

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

Shorecrasher Elemental

{U}: Exile Shorecrasher Elemental, then return it to the battlefield face down under its owner's control.
{1}: Shorecrasher Elemental gets +1/-1 or -1/+1 until end of turn.
Megamorph {4}{U} (You may cast this card face down as a 2/2 creature for {3}. Turn it face up any time for its megamorph cost and put a +1/+1 counter on it.)

Permafrost Trap

If an opponent had a green creature enter the battlefield under their control this turn, you may pay {U} rather than pay this spell's mana cost.
Tap up to two target creatures. Those creatures don't untap during their controller's next untap step.

Flooded Shoreline

{U}{U}, Return two Islands you control to their owner's hand: Return target creature to its owner's hand.

Snow-Covered Island

Icebind Pillar

{S}, {T}: Tap target artifact or creature. ({S} can be paid with one mana from a snow source.)

Winter's Chill

Cast this spell only during combat before blockers are declared.
X can't be greater than the number of snow lands you control.
Choose X target attacking creatures. For each of those creatures, its controller may pay {1} or {2}. If that player doesn't, destroy that creature at end of combat. If that player pays only {1}, prevent all combat damage that would be dealt to and dealt by that creature this combat.

Waterspout Elemental

Kicker {U} (You may pay an additional {U} as you cast this spell.)
Flying
When Waterspout Elemental enters, if it was kicked, return all other creatures to their owners' hands and you skip your next turn.