Nothing is uniform I'm afraid....
Buy a boat in the USA (eg a 40 ft one) and you're up for 10% GST plus 5% duty (calculated to include delivery costs) unless the boat was built in the USA in which then there is no import duty, just GST. If the boat was built in Europe and you bought it second hand from the USA you would be up for the full 15%.
Clear as mud... Just like a Chinese free-trade agreement.