Jungle is the first level of Serious Sam 2.
After meeting with the Sirian Grand Council, Serious Sam is sent to a Simba village on the planet M'Digbo. At the end of the village, he find's Mental's forces beginning an assault on the village. He clears out the troops, then travels to a field, where APC 404 Dropships are dropping off more of Mental's forces. Sam clears them out, then travels through a gigantic monkey head statue to reach a river.
2. When you get past the valley with the Auto Shotgun, look right. You'll find a soccer/football field. Nearby is a tree with a soccer ball caught in it. Destroy the tree, grab the ball, and push it into a goal. After some fanfare, a Medium Armor will teleport in.
3. While at the field where Dino is found, follow the left wall. Eventually, you will find a switch hidden behind a tree. Use the switch and a secret area will open. Go into it and use the teleporter there. It will warp you to where Dino was found, but instead a much stronger version of Dino will appear.
4. In the last area, look for a waterfall on the left. Walk towards the waterfall, and you'll find a plank with a XPML30 Rocket Launcher on it. Shoot the wooden plank holding it up, and the Rocket Launcher will fall. Pick it up.