The Dark

Giant Shark

If Giant Shark blocks or is blocked by a creature that has taken damage this turn, Giant Shark gains +2/+0 and trample until end of turn. Giant Shark cannot attack unless opponent controls at least one island. Giant Shark is buried immediately if at any time controller controls no islands.

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