It may seem that way, because water will go in right? But it wont happen, because for water to get into the tank, air or fuel has to come out, and they cant, a little water may come in because of the air compressing underwater, but otherwise water will not be 'compelled' to come in because nothing can come out to allow water to take its place. Mine was full EVERY time I took it out, but I do a lot of subs and stuff so, it was a no brainer for me.