Basically correct, but if the marina wishes to connect to the canal then crt require that the marina must agree to only allow boats with a crt licence to stay. So if an unlicensed boat is in the marina crt can not take action against the boat/boater but the marina would be in breach of it’s agreement with crt, so crt can take action against the marina, for example by closing the marina access to the canal.
To avoid this situation the marina requires in it’s agreement with boaters that boats are licensed, if a boat is unlicensed then it’s the responsibility of the marina to enforce it’s agreement with the boater.