Carnivores: Cityscape Easter Egg - Rats Worshipping Serious Sam and Bird Teleporter

In the first human mission of the game there is a secret chamber at the bottom of the first lake you come to. It has rats worshipping a statue of Serious Sam, and some cave paintings of some of the developers of the game. It's very well hidden, and can be hard to get to without drowning (thought not impossible) so you might want to put on god mode ("please god" in the console).

1) Swim to the middle of the lake, directly above a large underwater rock. The waterfall should be directly behind you.
2) Dive straight down. Just past the rock, hidden among the reeds on the lake bed is a hole. NOTE: It is VERY hard to see. You may just want to push around on the lake bed till you pop in.
3) It is near to the rock, just past it if you are coming from the waterfall.
4) A very long tunnel follows. There is a health powerup partway through to help you survive.
5) If you make it through the severely narrow tunnels, you come out in a cave with a statue of Serious Sam (this game uses the Serious Sam Engine, so that explains this) and some rats surrounding it falling down repeatedly in front of it. There are pictures painted on the cave walls of some of the artists and designers from the game.
6) To Exit, walk around the statue. You should walk into a teleporter which teleports you into one of the dinosaur birds outside, killing the bird and dropping you from his position. If you've already killed the bird, you'll pop out at his last live position. This may be a good idea because if he isn't flying over the lake when you warp out, you may splatter on the ground from the fall.