A red Raptor rushes you. Fire as fast as you can and dodge this guy's attacks. When he is dead enter the valley and kill the second raptor. Check your health at this point and make sure its FULL. Note the broken rope bridge above. Note the HUGE FOOTPRINTS below. Note the tense music that just started playing. Note the size of the teeth on the T-Rex that just rounded the corner. Do a LOT of side-jumping and keep firing until this monster is dead. You may have to heal yourself in mid-combat. NEVER let this guy get close to you with his mouth or you are dead no matter what your health bar says.
After he is dead run past him under the bridge until you reach 2 waterfalls. Climb the ledge to the right of the right waterfall to find SECRET #1: Shotgun shells. Go to the ledge between the falls. Climb up 2 ledges and jump to the right onto the 3rd ledge. Hold onto the ledge and shimmy to the right until you're in the middle of the falls. Pull yourself up and into SECRET #2: Shells and Uzi Clips.
Return to the ground (climb or dive) and head for the broken bridge and look for a door in the grass covered rock. Enter the passage and kill the raptor waiting down the hall. Advance until you reach a waterfall. Climb the ledges to the right and get Cog #1. Then dive into the pool.
Swim until you surface at the right waterfall in the valley. Turn left and advance to the temple in the distance. Take out the 2 raptors lurking near the temple. Enter the temple and save your game. Take a swim heading for the right side of this pool to get Cog #2. Exit the temple and find a climbable ledge along the left valley wall near the dead raptors.
Climb the first ledge then jump left to the 2nd ledge. Turn left to jump (or grab) the 3rd ledge then do a leap and grab the 4th ledge. Do one more giant leap onto the temple roof for SECRET #3 and get the medkit, magnum clips, uzi clips, and shotgun shells. You can get back down by going left and jumping to the slanted cliff and sliding to the bottom. Turn to the right and climb into the cave in the valley wall.
Follow the tunnel and save your game. Continue until you reach the rope bridge. Do the giant leap and grab the other side of the bridge. Pull yourself up and continue over to get Cog #3. Do a safety drop to the valley floor and make your way back to the cave above the first huge waterfall (the beginning of this level).
Next is a series of jump crisscrossing the river. Miss one and you are going for a ride over the falls so BE CAREFUL! The final jump requires you to grab the edge and pull yourself up. Follow the tunnel and cross the bridge. Save your game before crossing then use the 3 Cogs on the wall then pull the lever. The dam shuts and the waterfall stops.
Do NOT cross the bridge but rather drop off the side and grab on. Shimmy left and drop onto a rock. Go up and turn left to SECRET #4 and get a medkit. Jump in the water and swim until you reach the dam. Turn left and pull yourself up onto the ledge. Find the skeleton and get their shotgun (they don't need it anymore). Jump back in the water and enter a tunnel. This is a very long tunnel but you will eventually surface into SECRET #5 with shotgun shells and a medkit.
Go through the door and jump onto the dry riverbed. Follow it to the waterfall (or rather where the waterfall used to be) and dive into the lake below. There is now a tunnel you can get to which used to be blocked by the waterfall. Enter the tunnel and open the door and EXIT!