Ooooh, HL2 is wicked! Better than Far Cry Instints IMHO. More thinking mans FPS than FCI. I have yet to be stuck in HL2 because everything that you need to progress in there in the enviroment with you. And the physics are very cool. I haven't got very far yet but I was in an area where there was a ledge just a bit too high to climb out of the water onto. Hmmm.
I swim down, looking for clues. A culvert with boards across it, surely heres another way out. I start hacking away at the boards, they break and up floats a big wooden cable spool. Hmmm again. I swim up, discover that I can stand on the spool and push it over to the ledge to climb up. It's a great example of how the physics engine is so awesome.