...it likely won't help when someone is stealing a boat, but a cheap tip from police can help with items on your boat....LABEL them.
I have bought millions of dollars of computer and lab equipment for my university lab and field studies over 30+ years there. Security in Seattle and U Washington was always lax. The UW even installed door locks that could be easily twisted open with a pipe wrench to make it easier for fireman to enter...but also easier for a thief to break in.
In all those years, only things not labeled were taken. I had brand new, expensive items left, and old, relatively worthless unlabeled items taken. New, labeled computers left, old, unlabeled ones taken. Security cables didn't help...they were simply cut.
The police department lent me a carbide marker. I now have several, and with the last breakin and everything labeled, nothing at all was taken.