Hydroform | Magic: The Gathering
Formats Hydroform is Legal in
Official Oracle Text for Hydroform
—Prime Speaker Zegana
Official Rulings for Hydroform
1/24/2013 : Hydroform doesn't affect the land's name or any other types, subtypes, or supertypes (such as basic or legendary) the land may have. The land will also keep any abilities it had.
1/24/2013 : Effects that modify power and/or toughness but don't set them to a specific value (like the one created by Giant Growth), power/toughness changes from counters, and effects that switch a creature's power and toughness will continue to apply. This may happen if the land was already a creature when Hydroform resolved.