Once again, common sense rules. I've paddled with my Sheltie/Dachshund mix in my cockpit and it has worked out well. However, I take him with me ONLY in protected coves; in calm weather; and usually within swimming distance of shore. The only slightly harrowing incident occurred when we were camping and paddling in the San Juan Islands of Washington in June, when the resident pods of Orcas were feeding nearby. Some of them swam close to us, and started blowing, which prompted my pup to start frantically barking! I was concerned that out of curiosity an orca would get too close for comfort, perhaps looking for an unusual snack, but they ignored us.
A good, safe time was had by all.