Dan
Contributor
My jon line is also my reef hook. The line is 6 feet long, made out of nylon, 1/4” diameter, used for rock climbing. It has 2 quick snap clips on both ends to clip on to D-rings. See its picture, below.Or, if you search google for that term, you'll find it sold from several sites, even Walmart, at various prices, some with free shipping. This site sells it for $4.06, $10.54 including shipping, but it may come from somewhere in Asia and take a few weeks. It doesn't say. https://www.aliexpress.com/i/4000034408753.html
I have used it when I dive in fast current situation like in Blue Corner, Peleliu Corner in Palau, Kandu diving in Maldives, The Channel in Maratua Atoll, Magic Mountain in Raja Ampat, Manta Alley in Komodo, etc.