Lake Amphibians and Renegades are not 6 seat planes. They will handle waves better than Cessna (185/206) floatplanes, however: If wave height is an operational concern, the waves are too big to go. You do not choose a GA seaplane based upon its ability to land in high waves, you choose the aircraft which will do the job on more calm water. Then you use your considerable experience to judge for each landing or takeoff, if the wave height will create a hazard, and carefully mitigate, if the wave height exceeds your or the aircraft capabilities.
This is one of the main reasons insurance can be very costly in seaplanes, the insurance company is betting upon the skill of a pilot to observe, judge and select a suitable water area every time. This is completely backward to an airport, where winds aside, anything which changes or affects the runway will probably be reported to the pilot. When I train in seaplanes like the Lake, or Cessna, I will train that more than 9" high waves should be making you rethink how badly you need to be on that water, knowing that the 50% judgement error that will be made thereafter, will hopefully keep the pilot away from the 12" waves, which are generally considered limiting for these aircraft. Many time too often, the new pilot has said "I can land on that", and I have told them that they cannot do it safely. Judging the difference between 9" and 15" high waves from 500 feet takes skill, and getting it wrong is bad. I was in a back seat of a 185 decades ago, in which the pilot got it wrong, and very costly damage resulted.
If there is a Caravan on floats available, it will be for hire (by which I mean with a pilot), not for rent for you to fly away on your own. You should expect that if you are hiring a Caravan pilot to take you to a body of water not familiar to them, they will express that operation as a "try" rather than assurance that they can get it before they see it. The Caravan will handle waves greater than 12" but not a lot more.