As to the sea plane rating requirements in Canada it is interesting that T.C. requires five solo take offs and landings but no flight test.
If nothing else removing the five solo T & L requirement and replacing it with a flight test with an independent examiner would lower the insurance costs for sea plane training.
Then again it can't be all that difficult a task to learn to fly one because a lot of us only had five hours training with no solo requirement to get our sea plane ratings.