SOLVED. Sci-fi: Children around the world begin to develop powers, starting with a boy named Milo who grows extremely large (city sized). Spoilers ahead. [s]

[Henry]

I read this book sometime in the mid 00's. The other powers I can remember are a pair of siblings who developed the ability to dive incredibly deep in the ocean (could hold their breath and withstand pressure)

SPOILERS




The powers turned out to be given by an ancient creature captive at the bottom of the ocean, in order to let humanity fight an incoming cosmic being. This being was named after the sound it made - I think it was called "The Roar". At the end of the series it was chained to the dark side of the moon rather than be killed

[Becca]

The Silver Child by Cliff McNish

[Henry]

Thank you!

[Kris]

Glad you found your book, Henry

The Silver Child (book 1) of the Silver Sequence series by Cliff McNish - Becca's find.