Who helped Jack and Annie?

The person that helped Jack and Annie was the Water knight. Jack, Annie, and Walter Knight are all fictional characters from the book Summer of the Sea Serpent. Mary Pope Osborne is the author of this book. Summer of the Sea Serpent was published on March 9, 2004.

The genre of the book is fantasy fiction, and it is apart of the Magic Tree House Merlin Mission Series. Summer of the Sea Serpent is the third book in the series before it came to the book titled Haunted Castle on Hallows Eve. After Summer of the Sea Serpent came the book Winter of the Ice Wizard.