Extremely VALID Question!!
For those involved with sea-exposed airplanes of any type, this is import. Heck yes. I di not drive a seaplane, but in past decades have 'landed' a few++ on fresh or brackish water. Protecting you airplane (floats or hull, per type) is critical. If one listens with care, the details are included in basic training.
1. After Every water landing, wash or rinse as much as possible.
2. At home, wash even better.
3. Especially with a Wet Hull Airplane, no matter where moored or parked, get it OUT of the water as often as possible, inspect, INSPECT again, and then repair even the hint of a hull defect. Clean and paint the contact surfaces as necessary - and never delay or compromise anything.
4. It may well fly just fine, but if the SOB floods, your 'flying boat' will sink, often faster than you can drain it or get it into the air. How many times have we heard these horrible tails?
5. STCs are available for most, to install an in-flight water dump. Not a bad idea, but make sure that it actually works and that the water hits the dump when CG is correct.
6. Keep it CLEAN! Did I already mention this? That means inside and especially outside. Over ten years, expect to spend a LOT more on cleaning and paint than do most aircraft owners. This expense will vary, but it you park in salt water, expect to clean and repaint every other year - at best.
Aquatic - hull or floats - is great fun. It also requires considerable skill and some extremely serious attention to maintenance.