Part Water

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

Phantasmal Terrain

Enchant land
As this Aura enters, choose a basic land type.
Enchanted land is the chosen type.

Dreamwinder

This creature can't attack unless defending player controls an Island.
{U}, Sacrifice an Island: Target land becomes an Island until end of turn.

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.

Tidal Warrior

{T}: Target land becomes an Island until end of turn.

Devouring Deep

Islandwalk (This creature can't be blocked as long as defending player controls an Island.)

Flow of Ideas

Giant Shark

This creature can't attack unless defending player controls an Island.
Whenever this creature blocks or becomes blocked by a creature that has been dealt damage this turn, this creature gets +2/+0 and gains trample until end of turn.
When you control no Islands, sacrifice this creature.

Convincing Mirage

Spire Golem

Affinity for Islands (This spell costs {1} less to cast for each Island you control.)
Flying

Dandân

This creature can't attack unless defending player controls an Island.
When you control no Islands, sacrifice this creature.

Levitation

Moonbow Illusionist

Flying
{2}, Return a land you control to its owner's hand: Target land becomes the basic land type of your choice until end of turn.

Pirate Ship

This creature can't attack unless defending player controls an Island.
{T}: This creature deals 1 damage to any target.
When you control no Islands, sacrifice this creature.

Sea's Claim

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

Serpent of the Endless Sea

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

Hammerhead Shark

This creature can't attack unless defending player controls an Island.

Sea Snidd

{T}: Target land becomes the basic land type of your choice until end of turn.

Island

Vodalian Serpent

Kicker {2} (You may pay an additional {2} as you cast this spell.)
This creature can't attack unless defending player controls an Island.
If this creature was kicked, it enters with four +1/+1 counters on it.

Floodchaser

This creature enters with six +1/+1 counters on it.
This creature can't attack unless defending player controls an Island.
{U}, Remove a +1/+1 counter from this creature: Target land becomes an Island until end of turn.

Spreading Seas

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

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.)

Miscalculation

Counter target spell unless its controller pays {2}.
Cycling {2} ({2}, Discard this card: Draw a card.)

Manta Ray

This creature can't attack unless defending player controls an Island.
This creature can't be blocked except by blue creatures.
When you control no Islands, sacrifice this creature.