Coral Barrier

Defender (This creature can't attack.)
When Coral Barrier enters, create a 1/1 blue Squid creature token with islandwalk. (It can't be blocked as long as defending player controls an Island.)

Skyclave Squid

Defender
Landfall — Whenever a land you control enters, Skyclave Squid can attack this turn as though it didn't have defender.

Stinging Lionfish

Whenever you cast your first spell during each opponent's turn, you may tap or untap target nonland permanent.

Gomazoa

Defender, flying
{T}: Put Gomazoa and each creature it's blocking on top of their owners' libraries, then those players shuffle.

Kraken of the Straits

Creatures with power less than the number of Islands you control can't block Kraken of the Straits.

Foil

You may discard an Island card and another card rather than pay this spell's mana cost.
Counter target spell.

Scourge of Fleets

When Scourge of Fleets enters, return each creature your opponents control with toughness X or less to its owner's hand, where X is the number of Islands you control.

Dormant Gomazoa

Flying
Dormant Gomazoa enters tapped.
Dormant Gomazoa doesn't untap during your untap step.
Whenever you become the target of a spell, you may untap Dormant Gomazoa.

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.)

Purple-Crystal Crab

When Purple-Crystal Crab dies, draw a card.

Thought Sponge

Flash
Thought Sponge enters 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.

Tidal Barracuda

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

Serpent of the Endless Sea

Serpent of the Endless Sea's power and toughness are each equal to the number of Islands you control.
Serpent of the Endless Sea can't attack unless defending player controls an Island.

Sea-Dasher Octopus

Mutate {1}{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 deals combat damage to a player, draw a card.

Island

Horseshoe Crab

Stormtide Leviathan

Islandwalk (This creature can't be blocked as long as defending player controls an Island.)
All lands are Islands in addition to their other types.
Creatures without flying or islandwalk can't attack.

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.)

Coral Atoll

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

Voracious Greatshark

Flash (You may cast this spell any time you could cast an instant.)
When this creature enters, counter target artifact or creature spell.

Sigiled Starfish

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

Oneirophage

Flying
Whenever you draw a card, put a +1/+1 counter on Oneirophage.

Shore Keeper

{7}{U}, {T}, Sacrifice Shore Keeper: Draw three cards.

Sealock Monster

Sealock Monster can't attack unless defending player controls an Island.
{5}{U}{U}: Monstrosity 3. (If this creature isn't monstrous, put three +1/+1 counters on it and it becomes monstrous.)
When Sealock Monster becomes monstrous, target land becomes an Island in addition to its other types.

Dreadship Reef

{T}: Add {C}.
{1}, {T}: Put a storage counter on Dreadship Reef.
{1}, Remove X storage counters from Dreadship Reef: Add X mana in any combination of {U} and/or {B}.

Spreading Seas

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

Tolarian Kraken

Whenever you draw a card, you may pay {1}. When you do, you may tap or untap target creature.

Into the Roil

Kicker {1}{U} (You may pay an additional {1}{U} as you cast this spell.)
Return target nonland permanent to its owner's hand. If this spell was kicked, draw a card.

Guard Gomazoa

Defender, flying
Prevent all combat damage that would be dealt to Guard Gomazoa.

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}.

Inkwell Leviathan

Trample
Islandwalk (This creature can't be blocked as long as defending player controls an Island.)
Shroud (This creature can't be the target of spells or abilities.)