Interesting situation. Sea planes were never covered in the various rules of the road section of captains school. I wonder if a commercial sea plane pilot is also required to possess a CG captains license.
On the water here in the states there is ultimately no such thing as "right of way" when two vessels collide. Learning which vessel is the stand on vessel in all sorts of various on the water scenarios is a big part of testing for a captains license, however at the end of the day the CG has an ultimate stipulation that basically states that in any potential scenario involving two vessels, BOTH captains are required to operate their vessel in a manner that avoids collision, and in the event of such neither will be let off the hook. Of course that's in the states, does not account for alcohol which is a big no no, and is just what we were taught. I've never gone through any such scenario first hand.
Interesting situation. I've honestly never considered sea planes on the water and where they fall into the rules of the road. We had to learn about all sorts of scenarios but none involved aircraft