I am sorry to hear about Dale's loss. My condolences go out to his family and friends. From what I have read, he was well liked and respected in the community.
There is very little information online about what happened. Some in the media call it a drowning while others make no specific comment. The wind record was fairly light as others have said. It is possible that the accident wasn't seen by anyone making understanding what happened a lot harder. Given the small amount of repeated information online, it isn't feasible to say much more at this time about causes from those sources.