A whale is huge and has a huge tail also known as a fluke. Hence, A whale tail pendant meaning is all about strength and power just like the tail of a whale.
The tail of a whale has enormous power hence, the whale tail pendant also represents brute strength and power. 
A Whale's tail provides great speed and agility to a whale and with the help of its tail, a whale can cover vast depths of the ocean in no time to catch its prey or swim.
-sterling silver 
-20 cms long chain