I'm not at all nautical, but I think 8.8m nicely matches the depth of Portsmouth harbour.

Don't you fancy falmouth? Plenty of room in carrick roads, and due to the hills either side, wind tends to be straight up the channel, from the south. Nice surroundings as well.

Take her out to sea and sink her just outside the national limit on some sand bar. Fill her guts with gravel and concrete. Instant island/airfield/tax haven.

Principality of Sealand - Wikipedia, the free encyclopedia