Hi David,
My mate was out there on the same day and said that it was mostly flat and glassy and then they came upon the washing machine area as well. He was trolling through this but couldn't keep up against the current so they decided to bring in the lines. He put his son on the wheel as he wound in the lines. As he was doing this a wave came out of nowhere that broached the boat. After that scare he looked behind to see another one coming and yelled at his son to hit the trottle and get the heck out of there.
They were in 15 to 20 metres, he hasn't seen it that bad before especially being so calm in most other places but apparently this does happen from time to time with the current pushing to go over into deeper water ans usually happens on the western side of the banks going south.
The lesson is you need to always be on the look out.