If you have a full  water world (i customized a superflat to make 2 layers of water and one bedrock) and if an enderman is on the only block above water, you can easily see that when a projectile hits an enderman, he will teleport briefly into the water without taking any damage. The water will also not quench the fire if the enderman is hit with a fire charge. 

Edit: Tested this on a "Void" superflat preset, and the enderman may tp off the island onto open air, however he will not fall, and I've even had one occurance where the enderman will be hit by the fire charge, tp off island, float with the fire that was supposed to be on him about 5 blocks above him.