Get a rocket or grenade launcher and go near a river or beach with fish. Shoot the fish with a rocket or grenade. The fish will fly out of the water and swim around in mid air. Go to any beach area. Swim a little bit underwater to find a school of fish, dolphin, or turtle in the shallow parts. Get back to the beach where you are neck deep in the water, but still able to use a weapon. Aim the rocket launcher in the part of water where you last saw the aforementioned aquatic life. Fire off a few rockets. If all goes well, you should see a splash on the surface of the water and whatever you shot will come out and start flying around in the air.