Well, you want a dog that is confident and something that can be conned into doing whatever. My GSD is a good camping dog. Pretty good off leash without much training, is confident and puts a lot of heart into doing what I want him to.
He is from working lines and has what I would consider to be a lot of prey drive, however, he doesn't go after things that I haven't imprinted him on first... for instance, he has no interest in ducks at the park, cats, etc. However, he will strain at the leash, choke, flail and scream if he sees something I've previously encouraged him to pursue, and I prevent him from getting it without giving him a "shut up and behave" command.
The prey drive is a great thing to have in a dog that is going to be encountering a lot of new situations because, for instance, if you want him in the canoe and he's never seen a canoe, you have just to pick up a stick, wave it around and he'll do anything for it without thinking. He's fun to be around because he's an eager beaver and will try anything for you.
Aside from that he's about 80-90 lbs (might be a bit big for what you're doing), athletic (can clear a 4-5 ft fence without touching, can make it into a dumptruck box from the ground, etc.) he's enduring (3 hours at the beach, running after the ball, dragging our shoes behind him, in 2 feet of water, he barely slowed down) and even when I get him truly tired, he will still try if I ask him to do something. In the house, he settles down and will stay settled down, even if he could use a real workout.
Well that was long winded. In summary, I would go for a breed that is know for being eager to please, and pick a pup that has decent prey drive and is completely confident in new surroundings.
Aesthetically pleasing too!
Our pace was boring him
Relaxing