Volunteers who want to be on the water can go to https://ironman.volunteerlocal.com/volunteer/?id=52424, enter the password "sup21", scroll down until they see the "SUPs and Kayaks" option, and select Friday and/or Saturday (Friday being the participant runthrough and Saturday being race day).
SUPs and kayakers will be the eyes and ears of the medical staff on the lake, and will also play a role in ensuring participants don't drift too far from the course markers. Ironman will send out a detailed PowerPoint a few weeks before the event that will answer most of your questions regarding equipment, course, timelines, etc.
If anyone has questions, they can reach out to me here at memphisironmanswim@gmail.com.
John Berger