Derek Rogerson 
The Secret of the Skull [EPUB ebook] 
The Brig Girls and the Skull Book 1

A chance meeting with a mysterious stranger over school lunch break sees six teenage friends dropped in at the deep end when they are given an assignment to save the world. Tasked with becoming caretakers of an ancient, and quite frankly grotty, skull, they must solve a cryptic clue that will lead them to their final goal – to save the world from an apocalyptic rise in sea levels. But there are creatures who will stop at nothing to try and stop the girls from succeeding, meaning our six face danger all the way. 

Will our girls and our World survive?