The first time I heard that there would be drivable vehicles in HL2, I was a bit skeptical. Vehicles just seemed a little too Unreal Tournament-ish for the Half-Life experience. Happily, I was completely wrong, and the vehicle chapters are just about my favorite parts of the game.

Water Hazard is great fun to play, in fact, it's probably the chapter I've played the most. You spend most of it fleeing at top speed while metrocops, APCs, and helicopters hound you at every turn. There are several places to stop and explore on foot, too, and it seems like every time I play I discover something new, some little ammo cache or hidden nook or some out-of-the-way bit of staging. The other night I was playing the level, and had gotten out of the airboat in a marshy area to poke around. As I was walking around, I startled some crows who'd been behind some reeds. They flapped away, and when I went over to where'd they'd been perched, I found the charred corpse of a citizen I'd otherwise have missed. Nice (though grim) little touches like that are part of what makes the game so rewarding to explore again and again.

Add in a couple more physics puzzles, some great music, and of course, the point in the chapter where you finally gain the means to fight back against those damn relentless choppers, and Water Hazard is just a blast, start to finish.