"Piranha Lake" is a job in "Vicious Voodoo" of Sly Cooper and the Thievius Raccoonus.
Walkthrough[]
You will have two minutes to light 25 torches with your swamp skiff's flamethrower. In order to get fuel for the flamethrower, you have to run over piranhas. Each piranha gives you one shot, and you can only hold five. Avoid running down individual fish, and instead try to run over multiple fish at a time. Press 
or 
to fire your flamethrower when aiming at a tiki torch. When all 25 torches are lit, the gate will open, and you can drive through it and collect the treasure key.
Video[]
Sly Cooper and the Thievius Raccoonus Walkthrough - Vicious Voodoo - Piranha Lake