Flavio the Thermal Fish is the first Guardian level in Cossack Village.
Jump into the Hot Air Balloon after speaking to the nearby Gobbo once the entrance to this stage appears near Swap Meet Pete's shop. You can fly the Balloon around the arena with the [L stick], and press and hold [X] to make Croc lower the Balloon. There will be an Ice Block somewhere around the arena at all times; lower Croc to it and he'll automatically pick it up. Just make it a controlled flight downward, because if Croc hits the ground, he'll lose a Heart.
Of course, Flavio doesn't care for your actions, so he'll spit water bubbles at you periodically. Simply stay in motion to avoid them. Once you pick up an Ice Block, press [Square] to drop it when you're over top of Flavio (watch your shadow to check your position). He'll retreat underwater. You must then pick up a second Ice Block and drop it into the water before Flavio re-emerges. Doing this will freeze the water, causing Flavio to pay up one point of damage. Do this three times, and you win. Flavio reappears more quickly each time, so waste no time in picking up the second Ice Block and dropping it in the water. Also, after each hit, Flavio fires more water bubbles before resting for a moment. All in all, though, this stage is quite simple. You receive 100 crystals for your victory.
Yippee! An image gallery for Flavio the Thermal Fish is available. Click here to access it.