Probably no one would ever steal one, but yeah, for $300, I lock mine to the power pole. I use that ring, and I’m pretty sure that’s what it’s for, with the cable lock in the link below. Takes about 30 seconds to lock or unlock. This isn’t the biggest cable lock around but there is no lock on earth that can’t be cut or broken with the big enough tools. Defeating this one would take some tools, a couple of minutes and some noise; someone walking by couldn’t just grab it - seems like the sweet spot to me.
Happened to me in Capreol last year. My Wifes Kayak. We had photos of it and plastered it all over facebook and i believe i posted it here as well. We ended up getting it back because we tracked it down ourselves and turned the heat up. Local law enforcement was a joke when it came to it. It was taken by some rather unsavoury people that have their hands in MANY dealings, which we reported to LEO's and they seemed to not give a shit. When we got it back, it was found in the bushed no more then 200m from their back yard....
As for ways to lock it up a simple cable lock should do. It can be put through the drain hole. Not fool proof, but still an inconvenience to anyone trying to steal it.
This is the way I handle robotic cells with failed door interlocks. The style I like to use is called Python Locks I think. Here is a link to an example on amazon.
You can get a python lock for cheap. I still wouldn’t leave it unattended though.
https://www.amazon.com/dp/B000XTPNZK/ wrap it around, pull it snug, bam, switch is locked to the dock.