You guys have the wrong idea. My brother's yellow lab came paddling with
me -- swimming alongside, right under the paddle blade, for up to a mile at
a stretch. I tried to stay close along shore, or in the shallows, so she
could run. Paddled about 5 miles on a couple occasions, no problem. I
think longer cruises would be possible, but would want a "Doggy PFD" just in
case.

....
I watched a Labrador Laden Chinook paddle past us in Conception Bay
yesterday. That beast was likely 70 Lbs . I would not recommend this
because he was in the open rear hatch and had things gone badly the
boat would have been a tough thing to self rescue. The paddler had lots
of company ( 4 other boats ) . It was a curiosity but there could have
been safety issues had the location not been benign.
Justin French has a Yellow Labrador retriever that sits on the back
hatch but that dog is increadible. ( 70 + Lbs ) .
Sorry as this sounds I would look at a poodle or a spaniel and stick
them in the cockpit. You could shove the dog down and close the sprey
deck around a small poodle or say a Brittany spanial , Both these dogs
have a work history around water,. ( The poodle was once a hunting dog
and retriever .)
I own a Lab. He is fine in a Old Town 169 canoe but I could not fit him
into any of my sea kayaks.
I hope this helps.
Alex