Most if not all UK estuaries, enclosed and inland waters and lakes have published speed limits. This may not be the case on the open sea, sea lochs and large inlets but it'll be pretty comprehensive. To exceed those limits you'll need the establishment of a marine aerodrome with defined boundaries, despite which all vessels have complete priority over you in your seaplane, or possibly a local exemption. Any enclosed water is privately owned and 'landowner's' permission is required just as it is anywhere else. There used to be one in the Solent near Calshott in the '70s and one in the Medway that lasted on charts into the early '80s I think. There may also be one on Loch Lomond and possibly one below Glasgow.
Taxiing will not absolve you from adhering to published speed limits elsewhere. As an aeroplane you're at the very bottom of the list as far as maritime priority and rights of ways go.
You might manage Fowey in your Catalina providing you pick a day when it is clear of yachts (which is never) but take it to Aberdeen and you can write it off before you've even landed. Even yachts don't survive there!
Last edited by meleagertoo; 1st March 2023 at 19:52.