My son and his girlfriend just adopted a rescue dog, a four year old 140 pound rotweiller, against my advice.  I told them that people do not just give up 140 pound dogs unless there is a problem.  They claim it is a sweet little kitten.  When I went over to be introduced, it came to the front porch and turned into a rotty.  When confronted with aggressive big dogs, my instinct is to choke them to death, I guess I'm kind of rotty like that too.  Anyway, I backed out before I did something silly.  I called my son later and told him me and Mr. Rotty needed to meet on my turf, not his, so I showed up and took it for a truck ride.  I wanted to try out a new gun I had anyway.  Well, the dog was perfectly behaved, wasn't gun shy, and seemed normal and even lovable.
However, I know it's not.  That dog is a loaded gun.  I wouldn't take him canoeing, or anywhere off leash. Whatever happened to that dog in his previous life is unknown to us, and I'm not sure if it will ever be normal.
I have tripped with many of my own dogs.  Some were excellent, others would not go on a trip again after their first outing.  My Brittney Spaniel had an inexplicable appetite for human excrement.  Let's just say that after his snack was over, and he belched a couple of times, he never went on another overnight trip.  My Siberian was the best canoe dog ever, but didn't like people.  Fortunately, where I trip, I never see people.  I would say if you were going in a big group, or even solo in area where there are lots of people, and your dog is not well behaved, leave him home.  
Here's a pick of my loveable little poop eater.
