Personally I’ve ended in the river while paddling an open canoe with a friend who was kneeling in the front and leaned over a bit too far to give it a bit of an extra pull.
The best however was my son who was out on a canal boat with his dog which was only a pup. He moored up for a day or so and the dog got used to jumping on and off the boat onto the bank and going walkies along the towpath on his own. One day my son went upstream for a few hours, turned round and came back and moored up in the same spot but facing the other way. Of course the dog decided to go walkies again, leaped off the boat as usual, straight into the canal instead of onto the towpath .The poor dog panicked and managed to paddle to the opposite bank and promptly got trapped in the mud and reeds.
Son had to jump into the canal, wade across to the other side through all the filth and mud to rescue his dog and get it back onto the boat