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

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

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.)

Phantasmal Terrain

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.

Hammerhead Shark

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

Tidal Warrior

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

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.

Miscalculation

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

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.

Spire Golem

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

Island

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.

Part Water

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

Flow of Ideas

Sea's Claim

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

Spreading Seas

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

Levitation

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.

Sea Snidd

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

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.

Dandân

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

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.

Devouring Deep

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