A couple things:

I pulled a Cat5 through 1/2" black poly. Used nylon chalk line tied to a wooden plug just a bit smaller than the inside of the poly. Sucked it through 200' with a shop vac, then pulled the cable with a spare chalk line back through. Didn't use any pull lube.

It is very hard to near impossible to keep water out of a length of poly running under ground. I'd seriously recommend using Cat6E direct bury cable so if/when it gets water inside the poly, you'll still be good.