Hydroblast

Choose one —
• Counter target spell if it's red.
• Destroy target permanent if it's red.

Stonybrook Banneret

Islandwalk (This creature can't be blocked as long as defending player controls an Island.)
Merfolk spells and Wizard spells you cast cost {1} less to cast.

Spreading Seas

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

Foil

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

Mist-Cloaked Herald

Sunken City

At the beginning of your upkeep, sacrifice this enchantment unless you pay {U}{U}.
Blue creatures get +1/+1.

Island

Rootwater Commando

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

Streambed Aquitects

{T}: Target Merfolk creature gets +1/+1 and gains islandwalk until end of turn. (It can't be blocked as long as defending player controls an Island.)
{T}: Target land becomes an Island until end of turn.

Enclave Elite

Multikicker {1}{U} (You may pay an additional {1}{U} any number of times as you cast this spell.)
Islandwalk (This creature can't be blocked as long as defending player controls an Island.)
This creature enters with a +1/+1 counter on it for each time it was kicked.

Brainstorm

Draw three cards, then put two cards from your hand on top of your library in any order.

Blue Elemental Blast

Choose one —
• Counter target red spell.
• Destroy target red permanent.

Triton Shorestalker

Flash Flood

Choose one —
• Destroy target red permanent.
• Return target Mountain to its owner's hand.