Finding water inside of the keel isn't unusual. The previous owner of my boat had screwed the bilge pump into the bilge. When we hit -30F, the keel's fiberglass developed a few cracks. Thankfully it wasn't a terribly complicated repair thanks to this forum.
Before I stored indoors I would drill three holes on each side of the keel at the end of the season. Some water would always come out. I would fill the holes come spring time.