It's skeg actually
They make removable ones for surf boards so that you can switch out different ones to tailor your ride to the conditions
I don't think that they have such things for canoes though
Normally you'd get a canoe with a keel for open water, one without for river running.
The simpler the outfit, the more skill it takes to manage it, and the more pleasure one gets in his achievements.” --- Horace Kephart