Giant Shark

Creature - Fish
Giant Shark can't attack unless defending player controls an Island. <CR>
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. <CR>
When you control no Islands, sacrifice Giant Shark.

Creature - Shark
Giant Shark can't attack unless defending player controls an Island. <CR>
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. <CR>
When you control no Islands, sacrifice Giant Shark.

Creature - Shark
Giant Shark can't attack unless defending player controls an Island. <CR>
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. <CR>
When you control no Islands, sacrifice Giant Shark.

Creature - Fish
Giant Shark can't attack unless defending player controls an Island. <CR>
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. <CR>
When you control no Islands, sacrifice Giant Shark.