Dreamwinder can’t attack unless defending player controls an Island.

{U}, Sacrifice an Island: Target land becomes an Island until end of turn.

Floodchaser enters the battlefield with six +1/+1 counters on it.

Floodchaser can’t attack unless defending player controls an Island.

{U}, Remove a +1/+1 counter from Floodchaser: Target land becomes an Island until end of turn.

Kukemssa Serpent 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 Kukemssa Serpent.

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.

{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.

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

Water Always Wins — Whenever The Flood of Mars attacks, put a flood counter on another target creature or land. If it’s a creature, it becomes a copy of The Flood of Mars. If it’s a land, it becomes an Island in addition to its other types.

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

Kicker {1} (You may pay an additional {1} as you cast this spell.)

When Tide Shaper enters the battlefield, if it was kicked, target land becomes an Island for as long as Tide Shaper remains on the battlefield.

Tide Shaper gets +1/+1 as long as an opponent controls an Island.