Both of those cards untap permanents in general which includes lands, creatures, enchantments, artifacts, and even planeswalkers, but many cards specialize in specific permanent types
Search your deck for up to 3 Water Energy cards, reveal them, and put them into your hand
Scourge of Fleets Scourge of Fleets works bestalmost exclusivelyin mono-blue decks, where it soft locks your opponents with cards like Thassa, Deep-Dwelling or Conjurer's Closet to prevent them from maintaining a board state
You can use it immediately as a removal spell, and many times, the activated ability will be relevant, especially against Commander staples like Swiftfoot Boots
But Cavern of Souls is the only one that has the clause that makes your creature spell uncounterable
Color identity is established before the game begins and doesn't change during the game, even if your commander becomes a different color