How rare will it be !? o.O
A new (and very rare) special mount can now be caught from Northrend fishing pools.
Coralshell Turtle - Summons and dismisses a rideable Coralshell Turtle. This is a very fast mount, both on land and in water.
I know its a Coralshell Turtle mostly because they added it to the One That Didn't Get Away Achievement for fishing.