I like horror set in confined spaces and expeditions, so that part was fun. I do have a few things that pissed me off:
1.

why the actual fuck did Aidan go back for the ring?? And lie about his oxygen every dive?? Mans should not have been there.  I think I might have preferred if he died, actually.

2. A lot of coincidental things saved a lot of people a lot of times,,,
3.

I don't love the cloth explanation, but I don't really know of one that I would have liked. I was wondering if they were hallucinating during the last couple dives or something like that.

I don't often read horror but, I love period and dual timeline books. This book was such a thrilling read and I loved how the narrative jumped between the modern day shipwreck exploration story and the days leading up to the ship sinking in the 1920s. A lot of suspense was created from knowing that the ship was going to sink but not how it was going to happen. The chapters are short and often leave you with a cliffhanger as they whip you back and fourth between the two timelines. 

I'm not a diver, but the descriptions of the mechanics of a dive this deep felt plausible and it seemed like Darcy had done a lot of research into how an expedition like this would work.

My only criticism is wishing the book would have followed more than one character in the 1920s. We get to know one of the crew members but I would have loved a passenger perspective as well. (Even if it would have come at the expense of the fast pace.) There were five divers plus two people aboard the ship in the modern day timeline so it felt a bit unbalanced with the 1920's narrative where we primarily followed one person.

Overall highly recommend this one! 

From Below is a bone-chilling and original horror novel with organic scares. I've always been fascinated by scuba-diving and underwater worlds, but Coates used our innate fears of drowning and being stranded in the sea against readers, frightening even me, who doesn't have a natural-born fear of water. The book was gripping the whole way through, and the switches between timelines and characters were the perfect length to hold suspense. I was thoroughly entertained by this haunting story and highly recommend it for other horror readers.