To get the Tigershark do the following.

First, Complete the whole game. (Defeat all the bosses from story)

Second, Go to Campbell Castle, here Jasmine will tell you all about the Tigershark.

Third, Go to Mumbi, you'll have to fight Sanjay because he's got the Tigershark.

When you beat Sanjay obtain the Tigershark, a new boss will appear.  His name is Nomad, he has more Tigersharks, but when he runs out he'll fight you with his Lvl. 12 Saphira.