Turtles are basically reptiles. They are characterized by a shell that develops from their ribs and serve as a protective cover.
The earliest known turtles date back to around 215 million... years and are therefore considered to be the oldest members of the reptile family.
The largest of turtles are aquatic though they do not lay eggs under water. They do breath under water though. When threatened these beautiful creatures can envelop inside their shells however, if rolled over they are very vulnerable.