Tidal Flats

{U}{U}: For each attacking creature without flying, its controller may pay {1}. If that player doesn't, creatures you control blocking that creature gain first strike until end of turn.

Viscerid Drone

{T}, Sacrifice a creature and a Swamp: Destroy target nonartifact creature. It can't be regenerated.
{T}, Sacrifice a creature and a snow Swamp: Destroy target creature. It can't be regenerated.

Submerge

If an opponent controls a Forest and you control an Island, you may cast this spell without paying its mana cost.
Put target creature on top of its owner's library.

Homarid Spawning Bed

{1}{U}{U}, Sacrifice a blue creature: Create X 1/1 blue Camarid creature tokens, where X is the sacrificed creature's mana value.

Homarid Warrior

{U}: Homarid Warrior gains shroud until end of turn and doesn't untap during your next untap step. Tap Homarid Warrior. (A creature with shroud can't be the target of spells or abilities.)

Coral Reef

Coral Reef enters with four polyp counters on it.
Sacrifice an Island: Put two polyp counters on Coral Reef.
{U}, Tap an untapped blue creature you control, Remove a polyp counter from Coral Reef: Put a +0/+1 counter on target creature.

Tidal Control

Cumulative upkeep {2} (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.)
Pay 2 life or {2}: Counter target red or green spell. Any player may activate this ability.

Chambered Nautilus

Whenever Chambered Nautilus becomes blocked, you may draw a card.

Viscerid Armor

Enchant creature
Enchanted creature gets +1/+1.
{1}{U}: Return Viscerid Armor to its owner's hand.

Deep Spawn

Trample
At the beginning of your upkeep, sacrifice Deep Spawn unless you mill two cards.
{U}: Deep Spawn gains shroud until end of turn and doesn't untap during your next untap step. Tap Deep Spawn. (A creature with shroud can't be the target of spells or abilities.)

Tidal Wave

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

Floodwater Dam

Svyelunite Temple

Svyelunite Temple enters tapped.
{T}: Add {U}.
{T}, Sacrifice Svyelunite Temple: Add {U}{U}.

Brine Seer

{2}{U}, {T}: Reveal any number of blue cards in your hand. Counter target spell unless its controller pays {1} for each card revealed this way.

Sand Silos

Sand Silos enters tapped.
You may choose not to untap Sand Silos during your untap step.
At the beginning of your upkeep, if Sand Silos is tapped, put a storage counter on it.
{T}, Remove any number of storage counters from Sand Silos: Add {U} for each storage counter removed this way.

Scent of Brine

Reveal any number of blue cards in your hand. Counter target spell unless its controller pays {1} for each card revealed this way.

Benthic Djinn

Islandwalk (This creature can't be blocked as long as defending player controls an Island.)
At the beginning of your upkeep, you lose 2 life.

Sand Squid

Islandwalk (This creature can't be blocked as long as defending player controls an Island.)
You may choose not to untap Sand Squid during your untap step.
{T}: Tap target creature. That creature doesn't untap during its controller's untap step for as long as Sand Squid remains tapped.

Tidal Influence

Cast this spell only if no permanents named Tidal Influence are on the battlefield.
Tidal Influence enters with a tide counter on it.
At the beginning of your upkeep, put a tide counter on Tidal Influence.
As long as there is exactly one tide counter on Tidal Influence, all blue creatures get -2/-0.
As long as there are exactly three tide counters on Tidal Influence, all blue creatures get +2/+0.
Whenever there are four or more tide counters on Tidal Influence, remove all tide counters from it.

Island

Flood

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

Sea Sprite

Snow-Covered Swamp

Homarid

Homarid enters with a tide counter on it.
At the beginning of your upkeep, put a tide counter on Homarid.
As long as there is exactly one tide counter on Homarid, it gets -1/-1.
As long as there are exactly three tide counters on Homarid, it gets +1/+1.
Whenever there are four or more tide counters on Homarid, remove all tide counters from it.

Flooded Woodlands

Green creatures can't attack unless their controller sacrifices a land for each green creature they control that's attacking. (This cost is paid as attackers are declared.)

Water Wurm

Water Wurm gets +0/+1 as long as an opponent controls an Island.

Walking Sponge

{T}: Target creature loses your choice of flying, first strike, or trample until end of turn.