Sealock Monster (THS) from Theros, available at 401 Games Canada.

• Rarity: Uncommon
• Finish: Normal
• Artist: Adam Paquette
• Card Text:
  Sealock Monster can't attack unless defending player controls an Island.
  5UU: 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.