A canoe can be tarred only when it is a suitable wooden or heritage-style craft and the tar is being used as a traditional surface treatment, not as a repair for structural leaks or damaged modern hull materials.
Tar belongs to older wooden boat traditions, not to every canoe. Fibreglass, plastic, inflatable, painted, or composite canoes generally need materials made for those hulls. Pine tar or boat tar is more relevant to wooden parts, traditional construction, display craft, or heritage projects where a tarred appearance and maintainable coating are intended.
On suitable wood, prepare the surface by cleaning, drying, and removing loose failing coatings. Brush a controlled coat into the timber and pay attention to end grain, seams, rails, and exposed fittings. Heavy tar on a hull can drag, smear, and stay soft, so the finish needs to be purposeful rather than simply thick.
Tar will not turn a weak canoe into a safe boat. Cracked planking, failed joints, loose fasteners, rotten timber, and structural damage need proper repair before any surface finish is considered. For a craft that will actually go on water, the finish should be compatible with the construction and the intended use.