This may sound graphic but i ate blueberries and 4 hours later pooped loose dark poop, i also seen blueberry skin floating on top? is this normal?

Yes: Check to see whether not you have allergies to blueberries for it to go through your system so quickly like that. If you chewed it a lot, then you'd see less skin visible there, but if you chewed it and swallowed it whole, then you are going to see what you are seeing now your poop. And people do have allergies to food that they commonly eat, and don't even realize it.

Yes: You are not absorbing the skin of the blueberries in the intestinal tract and it is being expelled in your bowel movements. There is nothing harmful about this. The blueberry is also staining the stool and turning it darker. If dark black stool persists despite not eating blueberries for several days , then it could indicate gastrointestinal bleeding and requires evaluation by a physician.