After the boat crashes, call in an air strike on the corresponding location. Run up to the beach and move to the right to find a small puddle at the right side of the beach. Stand in it briefly, then move towards the middle of the beach to find a smaller puddle. Stand in that puddle briefly, then move towards the far left side of the beach. Stand briefly in the puddle in the barb wire. After a few seconds, the screen will shake and you will hear strange voices before four lion statues rise out of the ground with alien ray guns in their mouths.
If you just stand in the last puddle and not the others, you will still hear the weird voices and get the ray guns.