Have

Apprentice Wizard

Grayscaled Gharial

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

Kasmina's Transmutation

Enchant creature
Enchanted creature loses all abilities and has base power and toughness 1/1.

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.

Ponder

Look at the top three cards of your library, then put them back in any order. You may shuffle.
Draw a card.

Caller of Gales

{1}{U}, {T}: Target creature gains flying until end of turn.

Kukemssa Serpent

This creature can't attack unless defending player controls an Island.
{U}, Sacrifice an Island: Target land an opponent controls becomes an Island until end of turn.
When you control no Islands, sacrifice this creature.

Capsizing Wave

Return target creature to its owner's hand. (Then exile this card. You may cast the creature later from exile.)

Sword Coast Serpent

This creature can't be blocked as long as you've cast a noncreature spell this turn.

Sword Coast Serpent // Capsizing Wave

Dandân

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

Island

Phantom Wings

Enchant creature
Enchanted creature has flying.
Sacrifice this Aura: Return enchanted creature to its owner's hand.

Mana Leak

Counter target spell unless its controller pays {3}.

Preordain

Scry 2, then draw a card. (To scry 2, look at the top two cards of your library, then put any number of them on the bottom and the rest on top in any order.)

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.

Sea's Claim

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

Sleight of Hand

Look at the top two cards of your library. Put one of them into your hand and the other on the bottom of your library.

Spreading Seas

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

Eel Umbra

Flash (You may cast this spell any time you could cast an instant.)
Enchant creature
Enchanted creature gets +1/+1.
Umbra armor (If enchanted creature would be destroyed, instead remove all damage from it and destroy this Aura.)

Sea Monster

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

Goggles of Night

Whenever equipped creature deals combat damage to a player, scry 1, then draw a card. (To scry 1, look at the top card of your library, then you may put that card on the bottom.)
Equip {2} ({2}: Attach to target creature you control. Equip only as a sorcery.)

Contact Other Plane

Roll a d20.
1—9 | Draw two cards.
10—19 | Scry 2, then draw two cards.
20 | Scry 3, then draw three cards.