Not Fort Knox, just a kayak, stored on the beach in a salt-water
environment.

Windsurfing shop nearby had a bunch of boards stolen couple years back
and the perp used bolt cutters on the cables.

What I am thinking is the smallest gauge chain that will resist
garden-variety, low-end Home Depot/Lowe's bolt cutters.

Is this realistic, or can low-end bolt cutters get through 3/8" chain
(the largest size I would consider). If so, I guess I would fall back
to the smallest chain that a pair of diagonal cutting pliers could not
cut.

Also, there is matching a padlock to the chain..... The padlocks I saw
at Home Depot today probably resist bolt cutters at least as much as
3/8" chain, but did not look all that robust in the context of salt
spray and blowing sand 24-7. Maybe some sort of bag around the lock?

Galvanized, of course....
--
Pete Cresswell