I have a 55lb thrust Minkota trolling motor that pushes my drift boat maybe 4 or 5 miles on a 12 volt battery. I have a solar panel too that helps keep it running on a long day.

That same motor might push a styrofoam/fiberglass surfboard or SUP board boat all day long.

Too bad I'm 2000 miles from my shop. I may have to move my shop down here, so up North is fishing only.

Or have a shop in both places. There are small one man trolling motor boats out there already. I haven't seen a totally minimalist DIY one built like a wide surfboard yet. If you already had the trolling motor the boat board would cost maybe 200 bucks or so.

I have a Minkota trolling motor so I'll do that. But these little DC motors are cheap.
This boat isn't the shape I want but it is a good example of how easy this whole process looks.

I envision an extra-wide SUP board with outrigger oarlocks so I can row home if my battery runs out. With an an electric motor at the rear end. Like I said above my Minkota gives me a good 5 lake miles in a big heavy wind-resistant drift boat. I take two batteries. When one runs out I know its time to head home.

The same battery would run a SUP board all day long.

https://www.youtube.com/watch?v=bgHQjpHtbVk

Here he puts thin plywood on top of styrofoam before glassing. I'm not sure why. I wouldn't. I'd sand and putty up the styrofoam so it contoured to shape. And then I'd glass it directly.

https://www.youtube.com/watch?v=V4PpDLaRaVU