How water resistant is a Nikon DLSR camera?

What would happen if I dropped one in a tub of water?

Check for weather sealed camera they can withstand rain! Even non weather sealed camera can withstand drops of the guy who answered before me is wrong if you don't believe me check on youtube search nikon and canon durability test even non weather sealed camera are very rough and tough!

To the best of my knowledge dropping any DSLR - whether Nikon, Canon, Sony, Pentax, Olympus - into a tub of water will damage the camera beyond repair. The higher-end DSLR cameras are Weather Sealed but definitely NOT water proof. So keep your entry-level DSLR away from water filled tubs and in out of the rain.

It'd be toast.

Entry level DSLRs are not water resistant in any way. A single drop of water in the wrong place can kill them. They usually tend to withstand a few drops (i've seen people use their Canon Rebels in light rain), but i wouldn't take that risk.

Higher tiers of cameras, such as the D7000, offer some weather seals, but they are merely weather resistant and unlikely to be killed by a bit of rain, not water proof.

Only the highest tier of cameras made by Nikon ($2000+) has a good chance to survive being fully submerged.

Note that the lens too has to be weather resistant - no point in having a weather resistant camera body if the water can come through a cheap lens.

@siddhant:
Entry level cameras *CAN* withstand a few raindrops. They don't do so reliably though, but merely at a high percentage of cases.
If there's e.g. A 5% chance that the raindrops will kill the camera, then that most likely won't get noticed in a single youtube test where one camera is subjected to that kind of test once. One would have to repeat that test 20 times for one camera to fail.
Still, you wouldn't want to take that risk in a real life situation with a camera that you paid for instead of having it sponsored by the manufacturer for that test - or would you?

Tests like the ones that you mentioned are meaningless due to the low number of test runs.

It would die and untimely death.