Where: Northwest part of the map. Giant crater in the ground signified by the purple plus symbol.
When: Disc 3. Mechat is obviously needed.
What to do: Take out the land shark AND do it without taking damage.
Recommendation: Fully upgrade the Mechat
WARNING - Make sure you don't complete it while there are missiles in the air cause after you defeat the shark, the game locks but the missiles keep on coming and hit you.
Again, this comes in two parts. Stage 1 and stage 2.
Stage 1 - Yellow Energy Bar
The first part starts off easy and gets tricky. The shark starts in front and drops a few mines now and then. Shoot the mines and keep the machine gun going in between. Hopefully you will have upgraded the Mechat so that the guns never overheat. After taking 75% of the sharks health, he will move to your left hand side and then fire about 4 missiles. Take these down and follow him to the back while continuing to fire the machine gun at him. Watch out for the rockets he launches as well, the split ones are tricky, one to the left and one to the right. Once the energy bar is empty, a cut scene will be triggered as he is about to fire his beam cannon.
Stage 2 - Red Energy Bar
After the very short cut scene, the shark will fire some more of those split rockets but sometimes with 3 or 4 missiles going across the screen. In between picking the missiles out the sky, fire the machine gun and missiles at the shark. Watch out for the super rocket attack which centralises about 10 down the middle. Just keep rinsing and repeating and take heed of the DOUBLE WARNING at the top and the achievement should unlock at the black screen after you kill the shark.