The Bobbsey Twins On The Deep Blue Sea is a children's book by Laura Lee Hope and part of the Bobbsey Twins series. The book was first published in 1918. The story follows the adventures of the four Bobbsey siblings - Bert, Nan, Freddie, and Flossie - as they embark on a summer vacation aboard their uncle's steamship, the Ocean Queen. The twins are excited to be going on such a grand adventure and look forward to exploring the ship, meeting new friends, and having fun in the sun. However, things take an unexpected turn when a valuable diamond necklace belonging to a wealthy passenger goes missing. The twins, who are always eager to solve mysteries, take it upon themselves to investigate and find the culprit. Along the way, they encounter a cast of suspicious characters, including a mysterious woman and a shady deckhand. As the voyage continues, the Bobbsey Twins face other challenges, such as rough seas and a dangerous storm. Through it all, they work together to overcome their fears and solve the mystery of the missing necklace. "The Bobbsey Twins On The Deep Blue Sea" is a fun and exciting adventure story that is sure to delight young readers. With its engaging plot, colorful characters, and nautical setting, it captures the thrill of a summer vacation and the excitement of exploring the high seas.