What does réglementation? say?
There is no international yachting licence. However, you can apply for the International Pleasure Craft Operator's Certificate, which is the official international translation of your boat licence. To apply for it, contact Maritime Affairs.
It is therefore the legislation of each country that will determine the validity or need for permits, depending on the type of vessel.
According to flag regulations, it is the nationality of the ship (its country of registration) that determines the legal status, not that of the owner or crew.
Example
Concretely, if you are sailing abroad on a French boat, French regulations apply. Conversely, if you are sailing abroad on a foreign boat, you must refer to the regulations of the country. Exception for Croatia, where even if you are sailing on your French boat, you must be in possession of a valid navigation permit and the CRR - Radiotelephony Restricted Certificate .
Which permit for which pays??
Here is a non-exhaustive list of countries in Europe where a licence is compulsory for sailing and motoring.
France, Corsica and overseas
A boat licence is mandatory for any boat with a motor power greater than or equal to 6 horsepower (4.5 kilowatts). This means that most sailboats do not require a permit.. .
The licence is mandatory for a sailboat of 6 m or more in length and a motorboat of more than 5 m in length with a power greater than 11.26 kilowatts.
To rent a boat, you will have to show your licence to obtain an equivalent one.
In Portugal
The licence is mandatory for both sailboats and motorboats.
In Italy
The licence is mandatory to sail on all types of sailboats and on a motorboat with a power greater than 20 horsepower.
A licence is required to rent any type of boat. It is even required to have two licences on board (so two people on board) but very often only one will suffice, the second will sign a discharge.
Croatia
The boat licence including the VHF radio licence - the CRR - is mandatory.
The case of the RRC
If you are sailing abroad and your boat has a VHF, you will need to carry the Radiotelephone Operator's Restricted Certificate (CRR). It is mandatory to be able to use it, whether in a motorboat or a sailboat.