A tortoise that withdraws into its shell is protecting itself (see Armor). From what do you feel the need to hide?
In Chinese and Hindu mythology, the tortoise carries the world on its back, and personifies endurance. What burdens are you earning for which you need support?
In Taoism, this is the symbol of cosmic and prophetic power. As such, a tortoise appearing in your dream may presage some positive spiritual developments.
From the story of the Hare and the Tortoise, this creature may become an emblem of persistence in your dreams (see Rabbit).
Japanese: A messenger from the gods of the sea, which equates to a bulletin from your subconscious, intuitive self. Watch and listen closely!