I found this video surfing youtube. I guess you can stand up paddle surf behind a boat. I kinda want to try this behind a jet ski but i doubt the wave will be big enough.
I also found this video of a guy doing stand up paddle surfing in white water rapids. He’s doing really well on balancing, especially when you notice that he doesn’t change his hand position while paddling on the left side of the board. I wonder what stand up paddle board he’s on?