Tentacles by Roland Smith (author) (UK edition)

Ever since Marty and Grace’s parents disappeared on an assignment for a nature magazine, they’ve been living with their Uncle Wolfe. He’s a scientist fascinated by cryptids – creatures that appear in myths but haven’t been proven to exist, like the Loch Ness Monster. Now Uncle Wolfe is planning an expedition to New Zealand to track down a rare giant squid. He’s rented a huge (and possibly haunted) ship for the trip! But someone on board is determined to sabotage the mission – and if Marty and Grace keeping poking their noses into things, they might end up as the saboteur’s next victims! Plunge into a terrifying underwater adventure in this gripping latest novel from the author of Jungle Hunters.