"The Land That Time Forgot" by Edgar Rice Burroughs is a fantasy novel first published in 1918. When a German U-boat and its captors are sabotaged off course during World War I, they discover Caspak, a mysterious island where prehistoric creatures still roam and evolution unfolds in strange ways. Stranded with dwindling supplies, the crew must navigate not only dinosaurs and primitive humans but also their own conflicts as they struggle to survive in this lost world.
Wikipedia page about this book: en.wikipedia.org/wiki/The_Land_That_Time_Forgot_(novel))