A kayak has a deck and hatches that keep most water out. A canoe doesn't. Paddle drip, splash, rain and bilge water all collect in the same hull as your gear, so anything that isn't sealed gets wet even on a calm day.
The bigger issue is the swim. Maryland's paddling guidance tells paddlers to expect to capsize and swim occasionally in a canoe, kayak, paddleboard or raft. When that happens, loose gear floats off. Kansas Wildlife and Parks puts the fix simply: tie down gear and distribute weight evenly.
Pennsylvania's Fish & Boat Commission adds that if you capsize, you should hold on to your boat unless it presents a life-threatening situation. In a calm capsize, a bag tied to the boat stays with you. If you have to let go of the canoe, anything that's tied to it goes with the canoe. That's why the bag setup splits in two.