On a rock bottom, those grappling anchors look like they'd work well. Shouldn't need a very big one for a canoe. It's too bad they don't have some thing rubber-coated so you wouldn't have a galvanized metal anchor clanking around in the canoe.
Ayuh,.... The smallest or 2nd smallest of those would be a nice size for a canoe,....
Dipped or painted with "Dip-it" tool handle coating will quiet it down in the boat,...
Wrapped with line, 'n stuffed into a bag would be even better,....
The draw-back is gonna be loosin' it when it gets hung up in the rocks,...
Back before I bought my ole tinbarge, I did
Alota canoe fishin',...
The only "Anchor" I carried was a big 2" / 3" spring clamp like a cabinet maker would use, to grab a branch along the shore,...
If I was gonna need an open water anchor, I'd grab a brick, or concrete block, or convenient rock, something I didn't care when I lost it,...
Never something I
"Bought",....