Hey, I'm looking for a PC game I watched my brother play in the early-to-mid 00's. As far as I can remember it was a FPS similar to Quake or Half Life. The part I remember the most is being in an outdoor area (though most of the game was in some sort of facility) with these little three-legged creatures hopping around. They weren't enemies, I remember them being kind of cute, but you could still gore them up pretty bad if you wanted to. They were kinda like rabbits or mini kangaroos. The area was fairly green and lush, I think surrounded by mountains, with some sort of shack/shed being the only structure. I also remember parts where you could go underwater and find items and stuff, and I think you could die by running out of breath. Oh, and this might be from a completely different game but I think the inside of the facility was some kind of abandoned laboratory or scientific research centre; I remember a part with dead scientists lying around everywhere and an alarm going off with a lady's voice counting down, and at the end of the countdown a door opens and the whole place gets swarmed with monsters. The inside was quite dim, there were a lot of alarms and red flashing lights. The monsters as I remember were fairly humanoid-looking, but I didn't watch him play the whole game. Any ideas?
That sounds an awful lot like the original Unreal.