You can fly dual in a Beaver at Kenmore Air in Seattle. I did my SES there. On a Super Cub though... it was a FUN airplane but much too powerful for the purpose of learning. It just jumps off the water. Then I went to Island Coastal Aviation close to Vancouver to really learn to fly floats. I flew 50 hours on a 160hp C172. It was a challenge to get it off the water every single time! The question is if you want to do it for fun or if you'd like to be confident after the course to actually fly on floats. I recommend at least 15 hours instruction because docking and beaching needs some time to learn.