Yes. A bong will shed heat from even a large TEC (peltier) and a heavily overclocked system, and remain at or below room temp (when built right).
BUT...it's not without it's drawbacks. The water can get funky pretty fast with algae and bacteria growing in it, it's a wonderfull dust collector, it needs water to be added daily (either by you or some other means), it raises the room's humidity level, and it constantly sounds like a man peeing in a bucket.
If you can design around these problems, then you'll have a nice cooler.
I had one, and it did a great job. The upkeep made me go back to using a radiator.
It's all about what you're prepared to put up with, and what you have room for. You also need to consider kids, friends (why is beer in my bong?), and pets.