Indulge my curiosity, please! Do riverine speed limits apply to floatplanes / seaplanes? If I rock up in my (hypothetical, alas) Catalina or Otter in (say) Fowey or Aberdeen then I'm going to need to travel faster than the usual limit of 6 knots to land or take off. Even just moving around, it might be difficult to go so slow.
I found this old thread
https://www.pprune.org/archive/index.php/t-417223.html but that doesn't really answer my question. That's more about where you can operate than speed limits.