After Mr. Eaton kindly identified another photo as a huntsman spider I went to the guide and read the article, which mentioned the females carrying an egg sack beneath them. I did not see any photos of females with egg sacks here but I think this is one. This specimen had somehow become stranded on a swimming raft anchored in the lake behind our house. It was dislodged by my kids swimming and I rescued it with a water toy and swam it back to shore. I am not confident enough to ID it myself without someone confirming but it looks like a match.