Currently reading a book about ship building it was interesting to read that even inland towns had to provide the monarch with a ship..... Henry 2 demanded one of Cambridge. Was this peculiar to an island nation? Sometimes several towns together had to come up with one and  the demand was not always fulfilled, either. This text is not interested in what happened about that. Perhaps the wrath of kings was less then than the fear of outgoing Presidents is today.

Shipmoney (or the opposition to paying it) was a major cause of the rift between king Charles I and parliament. John Hampden, a lawyer and wealthy landowner from Buckinghamshire, who also owned extensive lands in North America (commerce with which was protected by the royal navy) nevertheless chose to test a legal case in the 1630s against the king's writ to raise ship-money on an inland county such as Buckinghamshire and also without approval of parliament. Hampden lost the case but the highlighting of the issue which the case brought resulted in the Shipmoney Act being passed by parliament in 1640 abolishing ship-writs - i.e. the king's right to raise shipmoney in either coastal or inland counties without recourse to parliament.

I don't think that ship-writs were necessarily peculiar to island countries. For instance, in 1492 Ferdinand and Isabella of Spain issued a provision commanding the town of Palos in Andalusia to provide 2 caravels for Christopher Columbus and his proposed voyage to the Indies. The townsfolk refused. It was only when the wealthy Pinzon brothers (residents of the town) stepped in to fulfil the provision themselves that royal blushes were spared regarding this.