http://www.angelfire.com/az/rainbowbridge/nephilim.html
E.W.Bullinger elaborated Scripturally as well:
"But we read of the Nephilim again in Num 13:33 "there we saw the Nephilim, the sons of Anak, which come of the Nephilim". How could this be, if they were all destroyed in the Flood? The answer is contained in Gen 6:4, where we read: "There were Nephilim in the earth in those days (i.e. in the days of Noah); and also AFTER THAT, when the sons of God came in unto the daughters of men, and they bare children to them, the same became mighty men (Heb. gibbor, the heroes) which were of old, men of renown" (lit. men of the name, i.e. who got a name and were renowned for their ungodliness). So that, "after that", i.e. after the Flood, there was a second influx of these fallen angels, evidently smaller in number and more limited in area, for they were for the most part confined to Canaan, and were in fact known as "the nations of Canaan"."
much more of potential interest is at that link, but it is untested.
E.W.Bullinger is tested, and most often correct in his findings. Still, test everything.