Roaming Iceberg

Roaming Iceberg enters the battlefield tapped.
{t}: Add {w} or {u} to your mana pool.
{1}{w}{u}: Roaming Iceberg becomes a 2/4 white
and blue Elemental creature with freezing until end of turn. It's still a land. (Whenever this creature deals damage to a creature, tap that creature. It doesn't untap during its controller's next untap step.)