yes it does seem hydrophobic, what i do (this is how i ruined my camera trying to video this process)
is i fill up a 5 gal bucket with water or tea or a nutrient solution, all depends on what i want to introduce to the medium. i then take the plant in the container and set it in the bucket, it floats initially but begins to sink gradually, once the containrer drops to the bottom of the bucket and is completly submerged i watch for air bubble escaping the top, when i see no more bubbles i pick it up and let it drain out well. im not sure how many times im going to have to do this throughout my grow but it seems to work well.