Here are some options you could consider, depending on the context:
General:
* Fleet (often used for a group of ships, but could apply to canoes as well)
* Group
* Collection
More Specific:
* Flotilla (implies a larger, organized group of watercraft)
* Squadron (implies a smaller, organized group of watercraft)
* Paddles (a bit informal, but could work if you're emphasizing the method of propulsion)
Ultimately, the best collective noun depends on the specific situation and the desired effect.