All upgrades are free. Type in the cheats menu:
Your mission in this hilarious bloody game is to play as a a killer piranha fish and eat everyone in your way. Jump out of the water and attack the humans as you consume blood and gain weight. Use blood consumed to create a piranha army, upgrade for bigger fins, better spine, stronger jaws and tougher scales.
Use YOUR MOUSE to control the fish. MOVE YOUR MOUSE above the water to JUMP and ON the humans to EAT. Have fun!