The United Kingdom
, at least, has extended
this limit to ten miles. This caused some friction with the Principality of Sealand
at the time, which became enveloped by the limit. Sealand
retaliated by extending its own sovereign territory
out to 10 nautical miles.
BTW, the UK originally set the limit at 3 miles because that was the longest distance from which a cannonball could penetrate one foot of Oak.