Lost at Sea is the sixteenth book in the Mysteries of Cobble Hill Farm fiction series.Harriet Bailey-Knight can’t imagine a better way to spend a beautiful afternoon than taking a leisurely boat cruise with her husband. But when they discover a sailboat floating off the coast of White Church Bay with no one aboard except a barking dog, they can’t help but fear the worst. The watercraft belongs to a couple who are documenting their journey around the United Kingdom on social media. While His Majesty’s Coastguard races to find the missing people, Harriet ends up not only taking care of the dog but also uncovering clues that the authorities may have missed.Meanwhile, Harriet is introduced to Jim, a very old giant tortoise with peculiar markings on his shell. There is a rumor concerning a tortoise that went down in a shipwreck in 1881. Could this be him after so much time? Harriet will have to dive into the history of the shipwreck to identify this ancient animal!