Took a slight 'detour' from Mo Hyder . .
.. just finished book 3 (of 5) of the
Atlantia series by Dean Crawford
https://www.goodreads.com/series/143073-atlantia
Very impressed so far to be honest, and by halfway through book 2 I was starting to envisage it as a televised Sci-Fi series to rival 'The Expanse'
I'll be making further forays into the writings of Mr Crawford very soon