I was beach starting almost all of the time on longish boards - Bic Astro Rock 285cm long, 125L / F2 Phoenix 320cm long, 190L.
It surprised me that George Peck started unicycling as a winter fitness training method for his short board windsurfing.
Not because of the similarities between the two sports - dingy sailing sitting down in a comfy seat = mountain bike, or driving a car / sailboard = Unicycle adrenalin rush, or riding a motorcycle.
But because he lives in Alaska.
You spend a lot of time in the water on a short board, and the waters around Seward will be freezing cold.
There is a link to the video here in post #2.