Please see the link below:-
http://www.waterrecreatie.be/htmlEN/cursussen.php
Regulations for the sea off Belgium apply to vessels over 15 metres (49' 3") or capable of over 20km/hr (12.5 mph) only, and to
all vessels on the inland waters .
They have a voluntary qualification for inshore and offshore skippers but this is only mandatory for the vessels above.
One point of interest is that most of Europe has a mandatory requirement for a qualification for smaller vessel skippers on their inland waterways. The network of rivers and canals is extensive and from the huge vessels which use these waterways, and at the speeds they travel, the need for everyone to know exactly what they are doing is vital.
I am a Yachtmaster Offshore (Sail & Power) under UK regs and free to roam the seas, but I still need an additional endorsement (CEVNI) to navigate the inland waterways of Europe (but not UK inlands).
In addition there is an international 'Recreation Craft Directive' which sets standards of build for leisure craft and the number of people carried. This is divided into categories depending upon the sea conditions they are rated for. However there are no limitations on where these craft sail - though an insurance company might have a point of view if a claim arises!
Commercial operators and charter boats are in a totally different world though and hedged around with all manner of constraints.