Hi, Last summer was the first year as new above ground pool owners. To get winter ready we drained as we were supposed to, put all filters, etc away and covered. Earlier this year the cover blew off and now the water is horrible looking, dirty, nasty. We figured we would just drain, clean and start over but I have been told by some friends that we don't need to do that. My question is what do we need to do to get it clean without draining? Thanks for your time.