The Skin Diving Mystery, by Mary Adrian (epub/Kindle/pdf)
THE SKIN DIVING MYSTERY is the story of four boys and a girl who belong to a skin-diving club. They have a wonderful time studying shells and marine animals together. But one day, a rare shell discovered by one of the members disappears. Then they all must concentrate on Operation Rare Shell to get it back. Jerry's "Sea Animal Log" which is included at the back of the book.
"Mary Adrian's new book, The Skin Diving Mystery, should prove as popular as her previous nature mysteries." --The News-Palladium, Benton Harbor, Mich.
"For skin diving fans 8 to 12, there's a good mystery by Mary Adrian...The Skin Diving Mystery concerns itself with the loss of a rare shell after it was found by a member of the skin diving club." -- The Pittsburgh Press